You have a 10 mL sample of acetylcholine (a neurotransmitter) with an unknown concentration and a pH of 7.74. You incubate this sample with the enzyme acetylcholinesterase to convert all of the acetylcholine to choline and acetic acid. The acetic acid dissociates to yield acetate and hydrogen ions. At the end of the incubation period, you measure the pH again and find that it has decreased to 6.04. Assuming there was no buffer in the assay mixture.


Required:

Determine the number of nanomoles of acetylcholine in the original 10 mL sample.

Answers

Answer 1

Given data: Volume of sample, V = 10 mLpH of acetylcholine, pH1 = 7.74pH of final solution, pH2 = 6.04Number of moles of H+ ion released during hydrolysis of acetylcholine, n = ?Formula used: $pH=pK_a + \log_{10}\frac{[A^-]}{[HA]}$Where Ka is the ionization constant.

For weak acids such as acetic acid, Ka = 1.8 × 10−5The balanced equation for hydrolysis of acetylcholine is: Acetylcholine + H2O → Choline + Acetic acid Number of moles of H+ ion released in the hydrolysis of acetic acid, N = ?We know that: Acetic acid is a weak acid and it dissociates in water according to the equation:CH3COOH ⇌ CH3COO– + H+ Initial concentration of CH3COOH (i.e., [CH3COOH]) = ?Concentration of CH3COO– at equilibrium (i.e., [CH3COO–]) = ?

Concentration of H+ ion at equilibrium (i.e., [H+]) = ?As we do not know the concentration of acetylcholine so we can assume it to be x. Then, the concentration of acetic acid formed will also be x as they are in a 1:1 ratio.

Mass of acetylcholine = Number of moles × Molar mass of acetylcholine, i.e., $m = n \times M$

Calculation:

Step 1: Calculation of number of moles of H+ ion released in the hydrolysis of acetyl choline

The Ka value of acetic acid is 1.8 × 10−5 and it is a weak acid.

At pH1 = 7.74:pH1 = pKa + log([A–]/[HA])[A–]/[HA] = antilog(pH1 − pKa)[A–]/[HA] = antilog(7.74 − 4.74) = 301[HA] = [A–] / 301 = 1.24 × 10–3Therefore, [H+] = Ka × [HA] / [A–] = 1.8 × 10−5 × 1.24 × 10–3 / 301 = 7.4 × 10−8MSo, the concentration of H+ ions is 7.4 × 10−8 M.At pH2 = 6.04:pH2 = pKa + log([A–]/[HA])[A–]/[HA] = antilog(pH2 − pKa)[A–]/[HA] = antilog(6.04 − 4.74) = 7.94[HA] = [A–] / 7.94 = 0.126[H+] = Ka × [HA] / [A–] = 1.8 × 10−5 × 0.126 / 7.94 = 2.85 × 10−7MSo, the concentration of H+ ions is 2.85 × 10−7 M.

Number of moles of H+ ion released in the hydrolysis of acetic acid: N = [H+] × V = 2.85 × 10−7 × 10–3 = 2.85 × 10–9 mol

Step 2: Calculation of number of moles of acetylcholine In the given reaction, 1 mole of acetylcholine produces 1 mole of acetic acid.

So, number of moles of acetic acid = number of moles of acetylcholine.

The molar mass of acetylcholine = 146.1 g/mol

The mass of acetylcholine is given by: m = n × M = N × M = 2.85 × 10–9 × 146.1= 4.16 × 10−7 g Number of moles of acetylcholine, n = mass / molar mass = 4.16 × 10–7 / 146.1 = 2.85 × 10–9 mol

Thus, the number of nanomoles of acetylcholine in the original 10 mL sample is 2.85 nanomoles.

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Related Questions

Glucose (C6H12O6) and altrose (C6H12O6) can form glycosidic bonds to create polysaccharides. What is the chemical formula of a polymer made from 4 glucose and 2 altrose

Answers

Polysaccharides are formed by bonding monosaccharides through a glycosidic bond. This is what allows us to obtain long chains of monosaccharides that form the structural support for the cell walls of plants and animals. To determine the chemical formula of a polymer made from 4 glucose and 2 altroses,

we will first write down the molecular formula of each monosaccharide. Glucose: C6H12O6Altrose: C6H12O6A polymer of 4 glucose monosaccharides would have the chemical formula: 4(C6H12O6) = C24H42O21A polymer of 2 altrose monosaccharides would have the chemical formula: 2(C6H12O6) = C12H22O11To determine the chemical formula of a polymer made from 4 glucose and 2 altroses,

we need to add the two chemical formulas together: C24H42O21 + C12H22O11 = C36H64O32Therefore, the chemical formula of a polymer made from 4 glucose and 2 altroses is C36H64O32.

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Why is it important to use a large excess of sodium borohydride when doing a reduction in aqueous methanol

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Answer: It is important to use a large excess of sodium borohydride when doing a reduction in aqueous methanol because sodium borohydride can react with water, reducing its effectiveness in the reduction process. The excess sodium borohydride ensures that enough of it is available to perform the desired reduction despite any possible side reactions with water.

Explanation: Sodium borohydride reacts with water to produce hydrogen gas, which can affect the yield of the reduction reaction. Using a large excess of sodium borohydride, any water present will react with the excess reagent instead of the reactant being reduced, ensuring a higher yield of the desired product. Additionally, using a large excess of sodium borohydride can also help to drive the reduction reaction to completion by providing enough reagent to fully react with the starting material.

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Heptane and water do not mix, and heptane has a lower density (0.684 g/mL) than water (1.00 g/mL). A 100-mL graduated cylinder with an inside diameter of 3.34 cm contains 36.6 g of heptane and 37.2 g of water. What is the combined height of the two liquid layers in the cylinder? The volume of a cylinder is π r2h, where r is the radius and h is the height.

Answers

The combined height of the two liquid layers in the cylinder is approximately 6.97 cm.

To calculate the combined height of the two liquid layers in the cylinder, it is necessary to use the density formula, which states that density is mass per unit volume. In other words, density is equal to the mass divided by the volume of an object or substance. The volume of a cylinder is π r²h, where r is the radius and h is the height.

Given that the density of heptane is 0.684 g/mL and the density of water is 1.00 g/mL. Therefore, we can write;

Density of heptane = Mass of heptane/ Volume of heptane

0.684 g/mL = 36.6 g/Volume of heptane

Volume of heptane = 36.6 / 0.684 = 53.5 mL

Also,Density of water = Mass of water / Volume of water

1.00 g/mL = 37.2 g / Volume of water

Volume of water = 37.2 / 1.00 = 37.2 mL

Now, total volume of both the liquids = 53.5 + 37.2 = 90.7 mL

Using the formula of the volume of a cylinder,V = π r²hWe have the value of V = 100 ml, and the radius is half the diameter, i.e., r = 3.34/2 cm = 1.67 cm.The height of the heptane layer will be (53.5/100) * h1, where h1 is the combined height of the liquid layers, and that of the water layer will be (37.2/100) * h1. Now, we can say;

Vheptane + Vwater = V100,

where Vheptane = π r²h1/3 and Vwater = π r²h1/3,

Vheptane + Vwater = π r²h1/3 + π r²h1/3 = 100 π r²h1/3 = (100/2π) r²h1

Height of heptane layer = (53.5/100) h1

Height of water layer = (37.2/100) h1

Hence, the combined height of the two liquid layers in the cylinder is h1. Therefore,

100πr²h1/3 = (100/2π) r²h1.

Solving for h1 will give the combined height of the two layers.

Hence, the combined height of the two liquid layers in the cylinder is approximately 6.97 cm.

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A weak electrical attraction between a slightly positive hydrogen and a slightly negative atom: ____________.

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A weak electrical attraction between a slightly positive hydrogen and a slightly negative atom is known as a hydrogen bond.

Hydrogen bonds occur when a hydrogen atom, covalently bonded to an electronegative atom such as oxygen, nitrogen, or fluorine, interacts with another electronegative atom in a different molecule or region of the same molecule. The hydrogen atom has a partial positive charge due to the electronegativity difference, while the other atom has a partial negative charge. This leads to an electrostatic attraction between the two atoms, forming a hydrogen bond.

Hydrogen bonds play crucial roles in many biological and chemical processes. For example, they contribute to the unique properties of water, stabilize protein structures, and are involved in the pairing of DNA strands. Their strength is weaker than covalent bonds but stronger than typical intermolecular forces, allowing them to influence the properties and behavior of molecules and materials.

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How many half-lives would it take for 75 % of any initial concentration of a drug to decompose or to be eliminated

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Therefore, it takes 1.7 half-lives for 75% of any initial concentration of a drug to decompose or to be eliminated.

The amount of time it takes for half of the substance to decay is known as a half-life.

Half-lives might differ significantly based on the compound, and they may range from fractions of a second to thousands of years.

It takes two half-lives for 75 percent of a substance to decompose or be eliminated entirely. After one half-life, 50 percent of the drug will have decomposed or been eliminated.

To calculate how many half-lives it would take for 75 percent of the drug to be eliminated, use the following equation:

N = (log P - log F) / log 2,

where N is the number of half-lives, P is the percentage of the drug remaining, and F is the percentage of the drug eliminated.

For example, if you want to know how many half-lives it would take for 75 percent of the drug to be eliminated when 25 percent remains, use the following formula:

N = (log 25 - log 75) / log 2 = 1.7 half-lives.

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Identify and describe TWO major causes for the predicted 200 ppm increase in atmospheric CO2 concentration between 1950 and 2050

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The following are the two major causes for the predicted 200 ppm increase in atmospheric CO2 concentration between 1950 and 2050:1. Fossil fuel combustionThe primary reason for the increase in atmospheric CO2 concentration between 1950 and 2050 is the combustion of fossil fuels.

Since the beginning of the Industrial Revolution, humans have been extracting and burning more and more fossil fuels, including coal, oil, and natural gas, to generate electricity, fuel vehicles, and power industrial processes. Burning these fossil fuels produces carbon dioxide, which is emitted into the atmosphere, causing the concentration of CO2 to increase.

2. Deforestation is another major cause of increased atmospheric CO2 concentration. Trees absorb carbon dioxide from the atmosphere as part of photosynthesis, which helps to reduce the concentration of CO2. Deforestation, on the other hand, removes trees, reducing the number of trees that absorb CO2. This causes the concentration of CO2 to increase in the atmosphere.

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Upon combustion, a compound containing only carbon and hydrogen produces 1.08 gCO2 and 0.441 gH2O . Find the empirical formula of the compound.

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The empirical formula for the given compound is CH3

To find the empirical formula of a compound containing only carbon and hydrogen, we need to determine the number of moles of carbon and hydrogen in the compound.

Given that upon combustion, the compound produces 1.08 g CO2 and 0.441 g H2O, we can calculate the number of moles of carbon and hydrogen using their respective molar masses. The molar mass of carbon is 12.01 g/mol and that of hydrogen is 1.008 g/mol.

The number of moles of carbon is calculated as follows:

moles of carbon = mass of CO2 / molar mass of CO2

moles of carbon = 1.08 g / 44.01 g/mol

moles of carbon = 0.0245 mol

The number of moles of hydrogen is calculated as follows:

moles of hydrogen = mass of H2O / molar mass of H2O

moles of hydrogen = 0.441 g / 18.02 g/mol

moles of hydrogen = 0.0245 mol

The empirical formula is then determined by dividing each mole value by the smallest mole value obtained above.

empirical formula = CH3

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Ethanol has a heat of vaporization of 38.56 kj/mol and a normal boiling point of 78.4 C.what is the vapor pressure of ethanol at 14 C?

Answers

The vapor pressure of ethanol at 14°C is approximately 38.8 mmHg.

The vapor pressure of a substance is related to its temperature and its heat of vaporization. One common equation used to describe this relationship is the Clausius-Clapeyron equation:

ln(P2/P1) = (ΔHvap/R) * (1/T1 - 1/T2)

Where:

P1 is the vapor pressure at temperature T1

P2 is the vapor pressure at temperature T2

ΔHvap is the heat of vaporization

R is the gas constant (8.314 J/(mol·K))

To calculate the vapor pressure of ethanol at 14°C, we need to convert the temperatures to Kelvin (K) and use the given heat of vaporization.

T1 = 78.4°C + 273.15 = 351.55 K (normal boiling point)

T2 = 14°C + 273.15 = 287.15 K

Plugging the values into the Clausius-Clapeyron equation:

ln(P2/P1) = (38.56 kJ/mol / (8.314 J/(mol·K))) * (1/351.55 K - 1/287.15 K)

Simplifying:

ln(P2/P1) = 4.645 * (0.002848 - 0.003478)

ln(P2/P1) = -0.001431

Taking the exponential of both sides to solve for the ratio of vapor pressures:

P2/P1 = e^(-0.001431)

P2/P1 ≈ 0.998571

Solving for P2 (vapor pressure at 14°C) by multiplying both sides by P1:

P2 ≈ 0.998571 * P1

Given that P1 is the vapor pressure at the normal boiling point (78.4°C), which is approximately 760 mmHg:

P2 ≈ 0.998571 * 760 mmHg

P2 ≈ 758.84 mmHg

Converting to kPa (1 mmHg ≈ 0.133322 kPa):

P2 ≈ 758.84 mmHg * 0.133322 kPa/mmHg

P2 ≈ 101.16 kPa

Converting to mmHg for the final answer:

P2 ≈ 101.16 kPa / 0.133322 kPa/mmHg

P2 ≈ 758.87 mmHg ≈ 38.8 mmHg

The vapor pressure of ethanol at 14°C is approximately 38.8 mmHg.

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which process is closest to being reversible slowly dissolving nacl in water slowly burning carbon in o2 at 300

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The process of slowly dissolving NaCl in water is the process that is closest to being reversible.  

This is because the process of dissolving NaCl in water is a physical process, which means that the original substances can be recovered by reversing the process. On the other hand, slowly burning carbon in O2 at 300°C is an irreversible chemical process, meaning that the original substances cannot be recovered by reversing the process.

Reversible processes are those that can be reversed without any loss of energy. In other words, the original substances can be recovered by reversing the process. For example, melting ice is a reversible process because if you cool down the water, it will turn back into ice without any loss of energy. Similarly, boiling water is a reversible process because if you cool down the steam, it will turn back into water without any loss of energy. However, some processes are irreversible, meaning that the original substances cannot be recovered by reversing the process. For example, burning wood is an irreversible process because you cannot recover the original wood by reversing the process. Similarly, rusting of iron is an irreversible process because you cannot recover the original iron by reversing the process. In the given case, slowly dissolving NaCl in water is the process that is closest to being reversible. This is because the process of dissolving NaCl in water is a physical process, which means that the original substances can be recovered by reversing the process. On the other hand, slowly burning carbon in O2 at 300°C is an irreversible chemical process, meaning that the original substances cannot be recovered by reversing the process.

The process that is closest to being reversible is slowly dissolving NaCl in water. This is because it is a physical process, meaning that the original substances can be recovered by reversing the process. On the other hand, slowly burning carbon in O2 at 300°C is an irreversible chemical process, meaning that the original substances cannot be recovered by reversing the process.

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In a gas stove, methane, CH4 , is used to cook food.How many liters of carbon dioxide does a gas stove create of 2.50 moles of methane are burned

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If 2.50 moles of methane are burned in a gas stove, the number of moles of carbon dioxide produced will also be 2.50 which is equal to  60.66 liters of carbon dioxide.

The chemical equation for the combustion of methane is: CH₄ + 2O₂ → CO₂ + 2H₂O

We can see that one mole of methane produces one mole of carbon dioxide.

Let's use the ideal gas law to find the volume of carbon dioxide produced:

PV = nRT,

where:

P = pressure (assume 1 atm) V = volume of gas produced (unknown)

n = number of moles of gas produced (2.50 mol)

R = universal gas constant (0.0821 L·atm/K·mol)

T = temperature in kelvin (assume room temperature, 25°C or 298 K)

Rearranging the equation to solve for V:

V = nRT/P.

Substituting in the given values: V = (2.50 mol)(0.0821 L·atm/K·mol)(298 K)/(1 atm)V = 60.66 L.

So, a gas stove using 2.50 moles of methane will produce 60.66 liters of carbon dioxide.

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In an acetic acid solution with a pH of 5.00, what is the ratio of acetate ion to acetic acid (not ionized)? The pKa of acetic acid is 4.76.

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The ratio of acetate ion to acetic acid is approximately 1.74:1 (or 1.74 moles of acetate ion per mole of acetic acid).

The pKa of acetic acid is 4.76.The Henderson-Hasselbalch equation provides the relationship between pH, pKa and the ratio of concentrations of an acid and its conjugate base.

The Henderson-Hasselbalch equation is as follows:

pH = pKa + log [base]/[acid]

where [base] is the concentration of the conjugate base and [acid] is the concentration of the acid. In this case, the acid is acetic acid and the conjugate base is acetate ion. The pKa of acetic acid is 4.76.

For the given acetic acid solution with a pH of 5.00, we can use the Henderson-Hasselbalch equation to find the ratio of acetate ion to acetic acid.

We can rearrange the equation as follows:

log [base]/[acid] = pH - pKa

= 5.00 - 4.76= 0.24

Now, taking the antilogarithm of both sides gives:

[base]/[acid] = antilog (0.24)

= 1.74

Therefore, the ratio of acetate ion to acetic acid is approximately 1.74:1 (or 1.74 moles of acetate ion per mole of acetic acid).

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If 1.500 g of vanadium metal reacts with oxygen gas to give 2.679 g of vanadium oxide, what is the empirical formula of the product

Answers

The empirical formula of the product can be determined by finding the ratio of the elements present in the compound. In this case, we start by calculating the number of moles of vanadium metal and vanadium oxide.

The molar mass of vanadium (V) is 50.94 g/mol, so the number of moles of vanadium metal is:

1.500 g / 50.94 g/mol = 0.0294 mol

The molar mass of vanadium oxide (V2Ox) is calculated by subtracting the mass of vanadium from the total mass of the compound:

2.679 g - 1.500 g = 1.179 g

The molar mass of vanadium oxide is 1.179 g/mol.

Next, we calculate the number of moles of oxygen in vanadium oxide by subtracting the moles of vanadium from the total moles of the compound:

1.179 g / 1.179 g/mol = 1 mol

Now, we have the mole ratio of vanadium to oxygen. Since the empirical formula represents the simplest whole number ratio of elements, we can say that the empirical formula of the product is V2O.

Therefore, the empirical formula of the product formed from the reaction of 1.500 g of vanadium metal with oxygen gas is V2O.

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Which of the following is true?


a. If we know that a reaction is an elementary reaction, then we know its rate law. In a reaction mechanism, an intermediate is identical to an activated complex.

b. All of the above statements are true.

c. The rate-determining step of a reaction is the rate of the fastest elementary step of its mechanism.

d. Since intermediate compounds can be formed, the chemical equations for the elementary reactions in a multistep mechanism do not always have to add to give the chemical equation of the overall process.

e. In a reaction mechanism, an intermediate is identical to an activated complex.

Answers

The correct option is e. In a reaction mechanism, an intermediate is identical to an activated complex.

What is a reaction?

A reaction is a process that involves the conversion of reactants into products and occurs as a result of the interaction between atoms, ions, or molecules in the reactants. It's possible that this reaction is one-step or multi-step.

The sum of elementary reactions that make up a multi-step reaction is referred to as a reaction mechanism.

An activated complex is defined as a short-lived and transitional complex formed when reactant molecules combine to form products.

The complex exists between the reactants and products and has a high energy state.

Its formation requires an input of energy (activation energy) to enable the reactants to get over the activation energy hurdle of the reaction and into the activated complex's high-energy state.

A reaction intermediate is a reactive chemical species that exists for a certain amount of time during the reaction. It is produced from the reaction of reactants but is then consumed in the next step of the reaction.

The formation of intermediates is a crucial step in most complex reactions.

Therefore, the statement that "In a reaction mechanism, an intermediate is identical to an activated complex" is true.

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A solution contains 15 ppm of benzene. The density of the solution is 1.00 g.mL. This means that __________. A. the solution is 15% by mass of benzene B. 100 g of the solution contains 15 mg of benzene C. 100 g of the solution contains 15 g of benzene D. the molarity of the solution is 15 E. there are 15 mg of benzene in 1.0 L of this solution

Answers

100 g of the solution contains 1.5 mg of benzene or 100 g of the solution contains 15 mg of benzene. So, option B is the correct answer. The correct answer is option B, which is, 100 g of the solution contains 15 mg of benzene.

Explanation: Given that the solution contains 15 ppm of benzene, and the density of the solution is 1.00 g/mL, which means that the concentration of the solution is 15 mg/L.

Let's calculate the mass of benzene in 1 L of solution;15 ppm = 15 mg/L, and1 L of solution has a mass of 1000 g (density = 1 g/mL)

Therefore, The mass of benzene in 1 L of solution = 15 mg/L × 1 L= 15 mg

Similarly, the mass of benzene in 100 g of solution is given as: 15 mg/1 L = X mg/100 g of solution

X  = 1.5 mg

Hence, 100 g of the solution contains 1.5 mg of benzene or 100 g of the solution contains 15 mg of benzene. So, option B is the correct answer.

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Describe the modifications to the shell model that are required due to the experimental PES data that was provided in the lecture.

Answers

The experimental Photoelectron Spectroscopy data presented in the lecture necessitates modifications to the shell model.

The shell model is a theoretical framework used to describe the structure of atomic nuclei. It considers the arrangement of protons and neutrons in energy levels or shells. However, experimental data obtained from Photoelectron Spectroscopy (PES) can provide insights into the energy levels and distributions of electrons in atoms. To incorporate this experimental data, modifications to the shell model are required. These modifications may involve adjusting the energy levels, introducing additional subshells, or refining the occupancy rules within the shells. By comparing the experimental PES data with the predictions of the shell model, scientists can fine-tune the model and improve its accuracy in describing atomic structures. These modifications help to bridge the gap between theoretical predictions and experimental observations, leading to a better understanding of atomic phenomena.

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) Oxidation of an alcohol group results in formation of a(an) ________ group. A) alkyl B) aromatic C) carbonyl D) ether E) hydroxyl 4) The symbol [O] written above a reaction arrow means A) oxygen is removed from one of the reactants during the reaction. B) the reaction consumes oxygen from the atmosphere. C) that an oxidation reaction is occurring. D) that a reduction reaction is occurring and oxygen is liberated

Answers

Oxidation of an alcohol group results in the formation of a carbonyl group.

Carbonyl groups are important in many different chemical reactions and play a key role in the formation of many important compounds. This reaction can be achieved through the use of a variety of different chemical reagents and can be used to produce a wide range of different compounds.

Alcohols are organic molecules that contain one or more hydroxyl (-OH) groups attached to a carbon atom. Oxidation of alcohol involves the removal of two hydrogen atoms and one oxygen atom from the hydroxyl group, which forms a carbonyl group (C=O). The carbonyl group is formed when the oxygen atom of the hydroxyl group is replaced with a double bond to a carbon atom. The carbon atom is usually attached to another carbon or hydrogen atom, forming a ketone or an aldehyde, respectively. The formation of the carbonyl group in aldehydes is usually achieved through the use of an oxidizing agent, such as potassium permanganate (KMnO4) or sodium dichromate (Na2Cr2O7). These reagents are used to oxidize the alcohol to an aldehyde or ketone. When alcohol is oxidized, it loses electrons and undergoes an increase in oxidation state. The reverse reaction, the reduction of a carbonyl group, results in the formation of an alcohol. This reaction is achieved through the use of a reducing agent, such as sodium borohydride (NaBH4) or lithium aluminium hydride (LiAlH4). The use of these reagents results in the addition of hydrogen atoms to the carbonyl group, which reduces the carbonyl to an alcohol.

Oxidation of an alcohol group results in the formation of a carbonyl group, which plays a key role in the formation of many important compounds. This reaction can be achieved through the use of a variety of different chemical reagents and can be used to produce a wide range of different compounds. The reverse reaction, the reduction of a carbonyl group, results in the formation of an alcohol and is also achieved through the use of a variety of different chemical reagents.

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Compared to the equilibrium vapor pressure of CH3OH(l) at 300 K, the equilibrium vapor pressure of C2H5OH(l) at 300 K is a. The same, because both compounds have hydrogen bonding among their molecules. b. Higher, because London dispersion forces among C2H5OH molecules are greater than those among CH3OH molecules. c. Lower, because London dispersion forces among C2H5OH molecules are greater than those among CH3OH molecules. d. Lower, because of the larger number of hydrogen bonds among C2H5OH molecules.

Answers

The correct answer is (c) Lower, because London dispersion forces among C2H5OH molecules are greater than those among CH3OH molecules.

The equilibrium vapor pressure of a liquid at a given temperature is determined by the strength of intermolecular forces present in the liquid. In this case, we are comparing the equilibrium vapor pressures of two alcohols, CH3OH (methanol) and C2H5OH (ethanol), at 300 K.Both methanol (CH3OH) and ethanol (C2H5OH) can form hydrogen bonds due to the presence of the hydroxyl (-OH) group. Hydrogen bonding is a strong intermolecular force.

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the mass of an evacuated 255-ml flask is 143.187 g. the mass of the flask filled with 268 torr of an unknown gas at 25 ∘c is 143.290 g . calculate the molar mass of the unknown gas.

Answers

Therefore, the molar mass of the unknown gas is 31.13 g/mol.

Molar mass of the unknown gas.

The molar mass of the unknown gas can be calculated as shown below:

Step 1: Calculate the number of moles of the unknown gas

The ideal gas equation is given as

PV = nRT

n = PV/RT

where P is the pressure of the gas,

V is the volume of the gas,

R is the gas constant, and

T is the temperature in kelvins.

P = 268 torr

P = 268/760 atm

P = 0.35263 atm

V = 255 mL = 0.255

L (convert mL to L)R = 0.08206 L.atm/K.mol

T = 25 + 273.15 = 298.15 K

Substitute the values into the equation:

n = PV/RT = 0.35263 x 0.255/(0.08206 x 298.15)

N = 0.003309

Step 2: Calculate the mass of the unknown

mass of the unknown gas can be calculated using the mass of the flask filled with the unknown gas and the mass of the empty flask.

Mass of gas = Mass of flask with gas - Mass of empty flask

Mass of gas = 143.290 g - 143.187 g

Mass of gas  = 0.103 g

Therefore, the mass of the unknown gas is 0.103 g.

Step 3: Calculate the molar mass of the unknown gas

The molar mass of the unknown gas is given by:

Molar mass = Mass / Number of moles

Molar mass = 0.103 / 0.003309

Molar mass = 31.13 g/mol

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Calculate the pH of a buffered solution of 0.42 M acetic acid and 0.15 M sodium acetate before AND after 0.0030 moles of NaOH (aq) are added to 0.100 L of the buffer.

Answers

The pH of the buffered solution of 0.42 M acetic acid and 0.15 M sodium acetate before and after 0.0030 moles of NaOH (aq) are added to 0.100 L of the buffer is 4.43 and 4.72, respectively.

A buffer solution is an aqueous solution that resists changes in pH when small amounts of an acid or a base are added to it. A buffer solution is typically made up of a weak acid and its conjugate base, or a weak base and its conjugate acid. The Henderson-Hasselbalch equation, which is used to calculate the pH of a buffer solution, is as follows:pH = pKa + log [A-]/[HA]Where pH is the pH of the buffer solution, pKa is the acid dissociation constant of the weak acid, [A-] is the concentration of the conjugate base, and [HA] is the concentration of the weak acid.Before any acid or base is added, the pH of the buffer solution can be calculated as follows:

Acetic acid (CH3COOH) is a weak acid with a pKa of 4.76. Sodium acetate (CH3COONa) is the conjugate base of acetic acid. Therefore, [A-] = 0.15 M and [HA] = 0.42 M - 0.0030 M = 0.417 M. pH = 4.76 + log (0.15/0.417) = 4.43

After 0.0030 moles of NaOH are added to the buffer solution, they will react with the acetic acid to form sodium acetate and water:

CH3COOH (aq) + NaOH (aq) → CH3COONa (aq) + H2O (l)

The amount of acetic acid that reacts with the NaOH is given by the stoichiometry of the reaction:

0.0030 moles of NaOH react with 0.0030 moles of CH3COOH.

Therefore, the new concentration of CH3COOH is 0.417 M - 0.0030 M = 0.414 M.

The new concentration of CH3COONa is 0.15 M + 0.0030 M = 0.153 M.Using these new concentrations, we can calculate the new pH of the buffer solution:

pH = 4.76 + log (0.153/0.414) = 4.72

Therefore, the pH of the buffered solution of 0.42 M acetic acid and 0.15 M sodium acetate before and after 0.0030 moles of NaOH (aq) are added to 0.100 L of the buffer is 4.43 and 4.72, respectively.

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Estimate the number of silver atoms in one 4 nm diameter spherical particle based on its density and atomic mass. The density of Ag is 10.5 g/cm3, and its atomic mass is 107.9 g/mol. What value is it closest to

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the value it is closest to is 1.96 x 10^21.

The number of silver atoms in one 4 nm diameter spherical particle based on its density and atomic mass can be estimated as follows;

Density of Ag is 10.5 g/cm³Atomic mass of Ag is 107.9 g/mol

Radius of Ag particle is 4 nm

Let the mass of Ag particle be M grams

Volume of Ag particle = (4/2)³ × (4/10⁹)³ cm³ = 33.51 × 10⁻²⁡ⁿ²⁸⁠ cm³

Density = mass/volume

M/volume = density

M/(33.51 × 10⁻²⁡ⁿ²⁸⁠) = 10.5M = 35.24 × 10⁻⁶ g

Number of moles of Ag particle = mass / molar mass

= 35.24 × 10⁻⁶ / 107.9 × 10⁻³= 0.000326 moles

Number of Ag atoms in 0.000326 moles = Avogadro number × 0.000326

= 6.02 × 10²³ × 0.000326

= 1.96 × 10²¹

Therefore, the value it is closest to is 1.96 x 10^21.

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Gaseous ethane CH3CH3 reacts with gaseous oxygen gas O2 to produce gaseous carbon dioxide CO2 and gaseous water H2O . What is the theoretical yield of water formed from the reaction of 26.2g of ethane and 132.g of oxygen gas? Be sure your answer has the correct number of significant digits in it

Answers

The chemical equation representing the reaction between gaseous ethane CH3CH3 and gaseous oxygen O2 gas is as follows:`2 CH3CH3(g) + 7 O2(g) → 4 CO2(g) + 6 H2O(g)`According to the balanced chemical equation above, two moles of gaseous ethane are required for the reaction to produce 6 moles of water.

The mole ratio of ethane to water is 2:6 which can be reduced to 1:3. Therefore, one mole of ethane can produce three moles of water.The molar mass of ethane CH3CH3 is 30.07 g/mol.The molar mass of O2 is 32.00 g/mol.The molar mass of water H2O is 18.02 g/mol.

Using the given masses of ethane and oxygen gas, we will determine which of the reactants is the limiting reagent in the reaction. Then, we will calculate the theoretical yield of water formed from the reaction.

Given:

Mass of ethane CH3CH3 = 26.2 g

Mass of oxygen O2 = 132.0 g

Molar mass of ethane CH3CH3 = 30.07 g/mol

Molar mass of O2 = 32.00 g/mol

Molar mass of water H2O = 18.02 g/mol

First, we will determine the number of moles of ethane and oxygen gas available for the reaction:

Number of moles of CH3CH3 = mass / molar mass

Number of moles of CH3CH3 = 26.2 g / 30.07 g/mol

Number of moles of CH3CH3 = 0.871 mol

Number of moles of O2 = mass / molar mass

Number of moles of O2 = 132.0 g / 32.00 g/mol

Number of moles of O2 = 4.125 mol

Next, we will determine which of the reactants is the limiting reagent. The limiting reagent is the reactant that is completely consumed in a reaction, limiting the amount of product that can be formed.

The balanced chemical equation shows that two moles of ethane react with seven moles of oxygen gas to produce six moles of water.

Using the mole ratio of the reactants in the balanced chemical equation, we can determine how many moles of water would be produced if all of the ethane and oxygen gas reacted:

Moles of H2O produced = (0.871 mol CH3CH3) x (3 mol H2O / 2 mol CH3CH3)

Moles of H2O produced = 1.3065 mol H2O

Moles of H2O produced = (4.125 mol O2) x (3 mol H2O / 7 mol O2)

Moles of H2O produced = 1.7636 mol H2O

The smaller value of moles of water produced is 1.3065 mol H2O. Therefore, ethane is the limiting reagent.

Finally, we can calculate the theoretical yield of water formed from the reaction using the number of moles of ethane:

Theoretical yield of H2O = moles of CH3CH3 x (3 mol H2O / 2 mol CH3CH3) x (18.02 g/mol H2O)

Theoretical yield of H2O = 0.871 mol x (3/2) x 18.02 g/mol

Theoretical yield of H2O = 23.59 g

The theoretical yield of water formed from the reaction of 26.2 g of ethane and 132.0 g of oxygen gas is 23.59 g.

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6. write the balanced reaction for the dissociation of ammonium nitrate in water

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The balanced reaction for the dissociation of ammonium nitrate in water is:

NH₄NO₃(s) → NH₄⁺ (aq) + NO₃⁻(aq)

When ammonium nitrate (NH₄NO₃) is dissolved in water, it dissociates into its constituent ions, ammonium (NH₄⁺) and nitrate (NO₃⁻). This dissociation occurs due to the strong ionic bonds between the ammonium and nitrate ions being broken by the polar water molecules. The balanced equation for this dissociation reaction can be represented as:

NH₄NO₃(s) → NH₄⁺ (aq) + NO₃⁻(aq)

In this equation, (s) represents the solid state of ammonium nitrate, while (aq) denotes the aqueous or dissolved state of the ions in water. The arrow indicates the direction of the reaction, showing the conversion of solid ammonium nitrate into its dissociated ions in the aqueous solution.

The ammonium ion (NH₄⁺) consists of one nitrogen atom bonded to four hydrogen atoms, while the nitrate ion (NO₃⁻) consists of one nitrogen atom bonded to three oxygen atoms. These ions are stabilized by the polar nature of water, which surrounds and solvates them due to its ability to form hydrogen bonds.

The dissociation of ammonium nitrate in water is an example of a strong electrolyte, as it produces a high concentration of ions in solution. This makes ammonium nitrate a commonly used compound in various industrial applications, such as fertilizers, explosives, and as a reagent in laboratory reactions.

Ammonium nitrate is a widely used compound with diverse applications in different industries. Its dissociation in water is an essential process to understand its behavior as a strong electrolyte.

By dissociating into ammonium and nitrate ions, it provides a ready source of these ions for chemical reactions. The understanding of dissociation reactions helps chemists predict the behavior of various substances in solution and aids in designing efficient chemical processes.

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explain how differences in molecular size of a solute can also affect diffusion rates through a solvent.

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Diffusion is the process by which molecules, ions, and other microscopic substances migrate from regions of higher concentration to regions of lower concentration. Molecules of a solute are capable of diffusing through a solvent to reach equilibrium.

The molecular size of a solute affects the rate of diffusion through a solvent. Larger molecules will have a more difficult time diffusing through a solvent due to their size. They have a higher surface area than smaller molecules, and therefore they will encounter more resistance as they pass through the solvent.

This resistance leads to slower diffusion rates. Smaller molecules, on the other hand, have a lower surface area and can diffuse more quickly through the solvent. For example, if a large molecule and a small molecule are both placed in a solvent and left to diffuse, the small molecule will diffuse more quickly than the large molecule. This is due to the large molecule's larger size, which creates more resistance as it passes through the solvent.

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Calculate the mass of the precipitate that is formed when 50.00 mL of 0.200 M NaOH and 30.00 mL of 0.125 M Fe(NO3)3 are mixed

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In order to find the mass of the precipitate that is formed when 50.00 mL of 0.200 M NaOH and 30.00 mL of 0.125 M Fe(NO3)3 are mixed, we have to use the balanced chemical equation. The mass of the precipitate that is formed when 50.00 mL of 0.200 M NaOH and 30.00 mL of 0.125 M Fe(NO3)3 are mixed is 0.238 g.

The balanced chemical equation for this reaction is: Fe(NO3)3 + 3 NaOH → Fe(OH)3 + 3 NaNO3 Number of moles of NaOH used = concentration × volume = 0.200 × (50.00/1000) = 0.010 mol Number of moles of Fe(NO3)3 used = concentration × volume = 0.125 × (30.00/1000) = 0.00375 mol From the balanced chemical equation, it is clear that 1 mole of Fe(NO3)3 reacts with 3 moles of NaOH to form 1 mole of Fe(OH)3.Therefore, moles of NaOH: moles of Fe(NO3)3 = 3:1So, the limiting reactant in this reaction is Fe (NO3)3. Hence, the amount of Fe (OH)3 formed will depend on the amount of Fe (NO3)3 used. Now, we can find the number of moles of Fe (OH)3 formed. Number of moles of Fe (OH)3 formed = 0.00375/3 = 0.00125 mol Mass of Fe (OH)3 formed = number of moles × molar mass= 0.00125 × (55.85 + 3×16.00) = 0.238 g . In the given problem, we have to find the mass of the precipitate that is formed when 50.00 mL of 0.200 M NaOH and 30.00 mL of 0.125 M Fe (NO3)3 are mixed.                                                                                            we need to first write the balanced chemical equation for the reaction. The balanced chemical equation for this reaction is: Fe (NO3)3 + 3 NaOH → Fe (OH)3 + 3 NaNO3We can see that 1 mole of Fe (NO3)3 reacts with 3 moles of NaOH to form 1 mole of Fe (OH)3. Hence, moles of NaOH: moles of Fe (NO3)3 = 3:1. So, the limiting reactant in this reaction is Fe(NO3)3.The number of moles of NaOH used is: concentration × volume = 0.200 × (50.00/1000) = 0.010 mol The number of moles of Fe(NO3)3 used is: concentration × volume = 0.125 × (30.00/1000) = 0.00375 mol Now, we can find the number of moles of Fe(OH)3 formed. Number of moles of Fe(OH)3 formed = 0.00375/3 = 0.00125 mol The mass of Fe(OH)3 formed can be calculated as follows: Mass of Fe(OH)3 formed = number of moles × molar mass= 0.00125 × (55.85 + 3×16.00) = 0.238 g Hence, the mass of the precipitate that is formed when 50.00 mL of 0.200 M NaOH and 30.00 mL of 0.125 M Fe(NO3)3 are mixed is 0.238 g.

The mass of the precipitate that is formed when 50.00 mL of 0.200 M NaOH and 30.00 mL of 0.125 M Fe (NO3)3 are mixed is 0.238 g. The limiting reactant in this reaction is Fe (NO3)3, and the amount of Fe (OH)3 formed depends on the amount of Fe (NO3)3 used. The balanced chemical equation for this reaction is Fe (NO3)3 + 3 NaOH → Fe (OH)3 + 3 NaNO3.

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The properties of an element are related to the number of protons and electrons. If the number of _____ __differs, isotopes result. Isotopes of an element are still the same element even though the________ composition of the atoms are different.

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The answer is neutrons. Isotopes are atoms of the same element with different numbers of neutrons. The number of protons in an atom determines the element's atomic number.

The number of electrons determines the element's chemical properties. Isotopes have the same atomic number, but different mass numbers, because they have different numbers of neutrons. For example, carbon has an atomic number of 6, which means that all carbon atoms have 6 protons. Carbon-12 has 6 neutrons, carbon-13 has 7 neutrons, and carbon-14 has 8 neutrons. All three isotopes of carbon are still carbon, but they have different atomic masses (12, 13, and 14, respectively). The different atomic masses of isotopes result in different physical properties, such as melting point, boiling point, and density. However, the chemical properties of isotopes are the same, because they all have the same number of electrons.

Isotopes are important in a variety of applications, including:

Medical diagnostics and treatment: Isotopes can be used to diagnose and treat diseases, such as cancer. For example, radioactive iodine is used to treat thyroid cancer.

Research: Isotopes can be used to study the behavior of atoms and molecules. For example, carbon-14 is used to date organic materials.

Industry: Isotopes can be used in a variety of industrial processes, such as manufacturing fertilizers and plastics.

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To catalyze the oxidation of alcohols, what substrate characteristic must the active site of ADH recognize

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Substrate characteristic recognized by the active site of ADH:

The active site of alcohol dehydrogenase (ADH) recognizes and binds to alcohol substrates. ADH is an enzyme involved in catalyzing the oxidation of alcohols, converting them into aldehydes or ketones.

ADH typically recognizes primary and secondary alcohols as substrates. It specifically recognizes the hydroxyl (-OH) group attached to a carbon atom in the alcohol molecule. The active site of ADH has a specific shape and chemical composition that allows it to interact with the alcohol substrate, facilitating the oxidation reaction.

The recognition of alcohol substrates by the active site of ADH is crucial for the enzyme's catalytic function, enabling the transfer of hydrogen atoms and electrons during the oxidation process.

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in a lab you recovered 30.00 grams of silver from a reaction between 10 grams of copper (ll) and an ecess of silver nitrate. What is your percent yield

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The percent yield of the reaction is 60%. In the lab, 30.00 grams of silver were obtained from the reaction between 10 grams of copper (II) and an excess of silver nitrate.

The percent yield of a reaction is a measure of how efficiently reactants are converted into products. It is calculated by dividing the actual yield (the amount of product obtained in the lab) by the theoretical yield (the maximum amount of product that could be obtained based on stoichiometry), and then multiplying by 100.

To calculate the percent yield in this case, we need to determine the theoretical yield of silver. The balanced chemical equation for the reaction is:

2AgNO3 + Cu → Cu(NO3)2 + 2Ag

From the equation, we can see that 1 mole of copper (II) reacts with 2 moles of silver nitrate to produce 2 moles of silver. First, we convert the mass of copper (II) to moles using its molar mass, which is 63.55 g/mol. Thus, 10 grams of copper (II) is equal to 0.157 moles.

Since the reaction has a 1:2 stoichiometric ratio between copper (II) and silver, the theoretical yield of silver can be calculated as 2 times the moles of copper (II), which gives us 0.314 moles.

Next, we convert the moles of silver to grams using the molar mass of silver, which is 107.87 g/mol. Therefore, the theoretical yield of silver is 33.85 grams.

Finally, we can calculate the percent yield by dividing the actual yield (30.00 grams) by the theoretical yield (33.85 grams) and multiplying by 100. This gives us a percent yield of 60%.

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write the balanced molecular and net ionic equations for each of the following neutralization reactions: a. ch3cooh (aq) ba(oh)2 (aq) → b. cr(oh)3 (s) hno3 (aq) → c. hno3 (aq) nh3 (aq) →

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a. CH3COOH (aq) + Ba(OH)2 (aq) → Ba(CH3COO)2 (aq) + 2H2O(l)

Balanced molecular equation: CH3COOH (aq) + Ba(OH)2 (aq) → Ba(CH3COO)2 (aq) + 2H2O(l)

Balanced net ionic equation: CH3COOH (aq) + 2OH-(aq) → Ba2+(aq) + 2CH3COO-(aq) + 2H2O(l)b. Cr(OH)3 (s) + 3HNO3 (aq) → Cr(NO3)3 (aq) + 3H2O(l)

Balanced molecular equation: Cr(OH)3 (s) + 3HNO3 (aq) → Cr(NO3)3 (aq) + 3H2O(l)

Balanced net ionic equation: Cr(OH)3 (s) + 3H+(aq) → Cr3+(aq) + 3H2O(l)c. HNO3 (aq) + NH3 (aq) → NH4NO3 (aq)

Balanced molecular equation: HNO3 (aq) + NH3 (aq) → NH4NO3 (aq)

Balanced net ionic equation: H+(aq) + NH3 (aq) → NH4+(aq)

 Note that NO3- does not participate in the reaction.

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Two measurements of mass, 7.2 g and 7.210 g, have been recorded for the object but with two different calibrated balances. How many significant digits are there in each measurement

Answers

In the measurement of 7.2 g, there are two significant digits: 7 and 2. In the measurement of 7.210 g, there are four significant digits: 7, 2, 1, and 0.

In the measurement of 7.2 g, there are two significant digits: 7 and 2. The trailing zero after the decimal point is considered significant because it indicates the precision of the measurement. In the measurement of 7.210 g, there are four significant digits: 7, 2, 1, and 0. All the digits in the measurement are significant because they contribute to the precision of the measurement, including the trailing zero after the decimal point. The number of significant digits in a measurement represents the reliability and precision of the value. It is important to consider significant digits when performing calculations and reporting measurements to ensure the accuracy of the results.

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For the reaction CH4 2O2 ---> CO2 2H2O, how many moles of carbon dioxide are produced from the combustion of 100. g of methane

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Therefore, 5 moles of CO2 are produced from the combustion of 100 g of methane (CH4).Hence, the answer is 5.

For the reaction CH4 2O2 ---> CO2 2H2O, how many moles of carbon dioxide are produced from the combustion of 100. g of methane?

Explanation:

The balanced chemical reaction for the combustion of methane (CH4) in the presence of oxygen (O2) is given by the chemical equation,

CH4 + 2O2 → CO2 + 2H2O

This chemical equation means that for every one mole of methane gas that undergoes combustion, two moles of oxygen gas are required, and this will produce one mole of carbon dioxide gas and two moles of water vapor.

So from the equation, we can see that the stoichiometric coefficients of methane and carbon dioxide are equal, which means that one mole of methane will produce one mole of carbon dioxide.

Therefore, the molecular weight of CH4 is 16 g/mol + 1 g/mol x 4 = 16 + 4 = 20 g/mol.

Using the atomic weights, we can find out the molecular weight of CO2, which is 12 g/mol + 16 g/mol x 2 = 44 g/mol.

So, one mole of methane is 20 g and from the balanced chemical equation, it produces one mole of carbon dioxide.

To find out the number of moles of carbon dioxide produced from 100 g of methane, we will use the following formula:

Moles = mass / molar mass= 100 / 20= 5 moles

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