Think critically...
Q7. Bridges are made from materials that contract and expand as the temperature changes, so
they cannot be fastened firmly to the bank of a river or lake. The photographs below show an
expansion joint at the end of a bridge in winter and in summer.
www
(A)
(B)
Which season is shown in each picture? Explain how you know?

At constant temperature and pressure the gibbs free energy value is a measure of the spontaneity of a process.

At constant temperature and pressure the gibbs free energy value is zero and when gibbs free energy value is zero then the process is spontaneous . The meaning of spontaneous  is that the process is takes place smothly with any effect and itself .

The Gibbs free energy also known as Gibbs function , Gibbs energy or free enthapy . It is a quantity that is used to measure maximum amount of work done in a thermodynamic system when temperature and pressure is keep constant.

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Answer: B: Your ears send a message through the nerves to the brain.

Answer:

B!!!!

Explanation:

hope this helps! :D

Answer:

B.) 117 g

Explanation:

(Step 1)

To find the mass, you need to first find the moles of NaCl using the molarity  ratio.

Molarity = moles / volume (L)

2.00 M = moles / 1.0 L

2.00 = moles

(Step 2)

Now that you know the moles, you can convert it to grams using the molar mass.

Molar Mass (NaCl): 22.990 g/mol + 35.453 g/mol

Molar Mass (NaCl): 58.443 g/mol

2.00 moles NaCl          58.443 g
---------------------------  x  -----------------  =  117 g NaCl
                                        1 mole

If the change in entropy of the surroundings for a process at 451 k and constant pressure is -326 j/k, then heat flow absorbed (in kj) by the system is -147.026kJ.

The entropy of particle is defined as how random it move. It shows the randomness of the system or may be disorders of the system. It is used to measure the unavailable energy for performing useful work.

Unit of entropy = J/K

∆s = ∆Q/T

where,

∆s = change in entropy of the surrounding = -326J/K

∆Q = heat absorbed from surrounding

T = Temperature = 451K

∆Q = ∆s × T

∆Q = -326 × 451

∆Q = 147,026 J

∆Q = 147.026 kJ

Thus we find that the heat absorbed by the system is 147.026 kJ.

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Answer: True

Explanation:

Out of the many tests that is used to determine the presence of cyclohexanol in a product is the Lucas test.

The Lucas test is a chemical reactant that is used to identify the presence and level of alcoholism in a given solution.  Cyclohexanol shows many chemical properties as do most substances, one of those property is the presence of an alcohol group.

The presence of this chemical group makes it possible to test for cyclohexanol using the Lucas test. The Lucas test will cause reactions in the presence of alcohol and convert alcohols into chloroalkanes, which is nearly insoluble in aquatic solutions.

From above, we concluded that a positive result will look like the solution separates into a cloudy chloroalkane-containing part on top of a much clearer layer.

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Answer:

(a) KCI

sylvine, is potassium chloride (KCl) in natural mineral form

The molar mass of the acid if 28. 5 ml of the koh solution is required to neutralize the sample is 90.23g/mol.

Molarity = (moles of solute/volume of solution) × 1000

Given,

Molarity of KOH solution = 0.180 M

Volume of solution = 28.5 mL

0.180 = (moles of KOH/ 28.5) × 1000

Moles = (0.18× 28.5)/1000

= 0.00513 mol

HA + KOH ------- KA + H2O

1 moles of KOH reacts with 1 moles of HA.

So, 0.00513 moles of KOH react with 0.00513 moles of HA.

Number of moles= given mass/ Molar mass

Given,

Mass of HA = 0.462 g

Moles of HA = 0.00512 mol

0.00512 = 0.462/ Molar mass

Molar mass = 90.23 g/ mol.

Thus the molar mass of HA required to neutralize the 28.5 mL of KOH is 90.23g/mol.

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The net ionic equation is written as H^+(aq) + OH^-(aq) -------> H2O(l)

The term net ionic equation refers to the equation that shows the ions that underwent a change in the reaction. We have to note that the reaction species here must be ionic species which are able to dissociate into ions in solutions.

Now the first step is to put down the molecular equation. The molecular equation shows the reaction of the compounds as follows;

HCI (aq) + NaOH (ag)-> NaCI (aq) +H2O(l)

Next, we put own the complete ionic reaction equation as follows;

H^+(aq) + Cl^-(aq) + Na^+(aq) + OH^-(aq) -------> Na^+(aq) + + Cl^-(aq) + H2O(l)

Next we have the net ionic equation;

H^+(aq) + OH^-(aq) -------> H2O(l)

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The only way increase the buffer capacity is to increase the total concentration of the system (conjugated acid + base).

The buffer capacity can be defined as the amount of strong base needed to change the pH of 1 liter of solution by 1 pH unit.

To increase buffer capacity to modify buffer solution-

The buffer capacity of a buffer, consisting of a weak acid and its conjugated base is given by the following equation:

π=㏑ 10 [{H⁺} + K ÷ H⁺ + CKα [H⁺]  ÷ [H⁺]  + Kα]

With [H^+] the concentration of the H^+ ion ; C the total buffer concentration (i.e. acid + conjugated base) and Kα the acidity constant.

It is clear from this equation that the buffer capacity is directly proportional to the concentration.

So the only way increase the buffer capacity is to increase the total concentration of the system (conjugated acid + base).

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The reading of mass so of hydrochloric acid involves sequence of analysis including:

The chemical structure of hydrochloric acid is HCl

Mass spectrometry is defined as a special analytical technique that is used to measure the mass ratio of ions.

It is used to determine the masses of atoms of chemical elements

So therefore, the reading of mass so of hydrochloric acid involves sequence of analysis including:

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1. The empirical formula of the compound is Ti₂O₃

2. The correct answer to the question is: smallest whole-number ratio of the atoms (Option C)

3. The correct answer to the question is: orange-brown (Option A)

4. The empirical formula of the compound is KClO₂

5. The empirical formula of the compound is P₂O₅

Divide by their molar mass

Ti = 66.6 / 48 = 1.3875

O = 33.4 / 16 = 2.0875

Divide by the smallest

Ti = 1.3875 / 1.3875 = 1

O = 2.0875 / 1.3875 = 3/2

Multiply by 2 to express in whole number

Ti = 1 × 2 = 2

O = 3/2 × 2 = 3

Thus, the empirical formula of the compound is Ti₂O₃

This is the simplest formula of a compound which shows the smallest whole number ratio of the atoms present in the compound

With the above definition, we can conclude that the correct answer to the question is: smallest whole-number ratio of the atoms (Option C)

In the tin oxide laboratory activity, the colour of the vapor emitted when nitric acid is added to the tin is: orange-brown

NOTE: This colour is visible when we carryout the practical experiment

Thus, the correct answer to the question is orange-brown (Option A)

Divide by their molar mass

K = 36.6 / 39 = 0.9385

Cl = 33.2 / 35.5 = 0.907

O = 29.9 / 16 = 1.8688

Divide by the smallest

K = 0.9385 / 0.907 = 1

Cl = 0.907 / 0.907 = 1

O = 1.8688 / 0.907 = 2

Thus, the empirical formula of the compound is KClO₂

Divide by their molar mass

P = 43.6 / 31 = 1.406

O = 56.4 / 16 = 3.525

Divide by the smallest

P = 1.406 / 1.406 = 1

O = 3.525 / 1.406 = 5/2

Multiply by 2 to express in whole number

P = 1 × 2 = 2

O = 5/2 × 2 = 5

Thus, the empirical formula of the compound is P₂O₅

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Answer:

1 cc always equals 1 mL.

Explanation:

The primary difference is that milliliters are used for fluid amounts while cubic centimeters are used for solids. No matter what is being measured.

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Acid nitric oxide

When a carboxylic acid combines with an acid chloride in the presence of a base, anhydrides are frequently produced.

The Fischer esterification, which involves reacting a carboxylic acid with an alcohol to produce an ester: RCO2H + R′OH RCO2R′ + H2O, is a well-known example of a dehydration reaction. The presence of a dehydrating agent, or a chemical that reacts with water, is frequently necessary for these processes.

Although an ester is produced when an acyl chloride and an alcohol react, this conversion cannot be stopped by adding HCl to the reaction mixture. One of the most popular carboxylic derivatives is esters.

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Number of significant figures will be 1.

Given:

weight of acetylsalicylic acid = 0. 4g

Significant figures are the digits of value which carry meaning towards the resolution of the measurement. They are also called significant figures in chemistry. All the experimental measurements have some kind of uncertainty associated with them.

When we convert 0.4g acetylsalicylic acid to mg we get value 400mg

when we convert 400mg to gram we get value of 0.4 gram

Since 0 before a decimal is not significant so there is only one significant figure that is 4.

It's an important story for a variety of reasons, and it comes at a time when people are looking to Hollywood more than ever to tell stories that represent them. Hidden Figures is that movie for many, and it's critical that everyone sees these women in action. This is why. This film tells a story that you've probably never heard before.

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Based on the half-life of the radioactive sample and the properties of nuclear reactions, the correct options are:

Half-life is the time taken for half the amount of atoms in an a radioactive element to decay.

1. After three half-lives, (1/2)³ of the original amount will remain = 1/8

1/8 of 16 = 2 ; option A

2. The balanced nuclear equation is given below:

action below:

/64 → /62 + 4He 2 ; option C

3. The trend of proton-to-neutron ratio as elements become heavier is that heavier elements have a greater amount of neutrons per proton; option C

4. The loss in mass of a compound composed of multiple atom types than those of the individual atoms they are made of is due to energy stored in the bonds in the nucleus known as the binding energy; option D

5. Initially, 12 g of carbon-14 was present

After one half-life, 6 g of carbon-14 remained, and 6 g of carbon-12 was present.

After two half-lives, 3 g of carbon-14 remained, and 9 grams of carbon-12 was present.

Age of the carbon sample = 5730 * 2 = 11460 years; option B

6.  A major argument against nuclear power plants is that they produce radioactive waste materials; option A.

7.  A common source of radiation that humans are exposed to come from outer space in the form of ultraviolet rays; option C.

8. The  balanced nuclear reaction is:

/92+/0 → /36+ 1/0 + 143Ba 56 ; option C

In conclusion, nuclear reaction results in changes in the nucleus of atoms.

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The weighted average of a penny is = 67.9g

The sample of penny for pre 1982 is a total of = 18 pennies.

The mass of each penny for pre 1982 = 3.1

Therefore the total weight for penny for pre 1982

= 18×3.1

= 55.8

The sample of penny for post 1982 is a total of = 32 pennies.

The mass of each penny for post 1982 = 2.5

Therefore the total weight for penny for post 1982

=32×2.5

= 80

The weighted average

= 55.8+80/2

= 135.8/2

= 67.9g

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The major product of reaction between 1-butanol and Na2Cr2O7 is butanoic acid.

When a primary alcohol like 1-butanol (OH is bonded to a primary carbon) is begin to oxidize in the presence of strong oxidizing reagent such as sodium dichromate (Na2Cr2O7) and H2SO4, sulfuric acid, the stepwise oxidation take place as above firstly to the corresponding aldehyde which undergoes further oxidation to the corresponding carboxylic acid.

You can find that the formed aldehyde after first oxidation is butanal and the only organic product, due to the strong oxidizing reagent is butanoic acid.

Thus, the major product formed is butanoic acid.

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The pH of the resulting solution is 2.05

Sodium hydroxide and hydrochloric acid neutralize each other in a 1:1 mole ratio as described by the balanced chemical equation

           [tex]NaOH_{(aq)} + HCL_{(aq)}[/tex] →  [tex]NaCl_{(aq)} + H_2O_{(aq)}[/tex]

This means that a complete neutralization, which would result in a neutral solution, i.e. a solution that has pH=7 at room temperature, requires equal numbers of moles of sodium hydroxide and hydrochloric acid.

Notice that your two solutions have equal molarities, but that the volume of the hydrochloric acid solution is 1.2 times larger than the volume of the sodium hydroxide solution. This implies that the number of moles of hydrochloric acid is 1.2 times bigger than the number of moles of sodium hydroxide.

This means that after the reaction is complete, you will be left with excess hydrochloric acid → the pH of the resulting solution will be <7.

Now, the number of moles of hydrochloric acid that will not take part in the reaction is given by

= moles of HCL added - moles of NaOH added

= 36 × [tex]\frac{0.100 moles HCL}{10^3 ml}[/tex] - 30 × [tex]\frac{0.100 moles HCL}{10^3 ml}[/tex]

= [tex]\frac{6* 0.100 moles}{10^3}[/tex]

The total volume of the resulting solution will be = ( 30 + 36 ) mL

                                                                            = 66 mL

Since hydrochloric acid is a strong acid that ionizes in a 1:1 mole ratio to produce hydronium cations, you can say that the concentration of hydronium cations in the resulting solution will be

[tex][ H_3O^+] = \frac{\frac{6*0.100}{10^3} }{66*10^3}[/tex]

[tex][ H_3O^+] = \frac{6*0.100}{66}[/tex]

pH = - log [tex](\frac{6*0.100}{66} )[/tex]

pH =  2.05

Therefore, the pH of the resulting solution is 2.05.

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The correct answer would be the structure attached of the form slant up, then run flat in a double bond, slant up and run flat.

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Answer:

D

Explanation:

Answer:

Fe(C₂H₃O₂)₃,  Fe(CN)₃,  Pb(C₂H₃O₂)₄,  Pb(CN)₄

Explanation:

Cations (positively charged ions) can only form ionic bonds with anions (negatively charged ions). However, you can't just simply put one cation and one anion together to form a compound. Each compound needs to been neutral, or have an overall charge of 0. When cations and anions do not have charges that perfectly cancel, you need to modify the amount of each ion in the compound.

1.) Fe(C₂H₃O₂)₃

-----> Fe³⁺ and C₂H₃O₂⁻

-----> +3 + (-1) + (-1) + (-1) = 0

2.) Fe(CN)₃

-----> Fe³⁺ and CN⁻

-----> +3 + (-1) + (-1) + (-1) = 0

3.) Pb(C₂H₃O₂)₄

-----> Pb⁴⁺ and C₂H₃O₂⁻

-----> +4 + (-1) + (-1) + (-1) + (-1) = 0

4.) Pb(CN)₄

-----> Pb⁴⁺ and CN⁻

-----> +4 + (-1) + (-1) + (-1) + (-1) = 0

The states of matter change to produce the same or the new substance. When yeast is added to hydrogen peroxide bubble of carbon dioxide is formed which indicates chemical change.

A chemical change is the formation of a new substance by the chemical alterations in the reactants. The yeast releases products of cellular respiration that react with hydrogen peroxide.

The reaction is exothermic as it releases heat and increases the temperature when measured by the thermometer. The Fizzing and bubbling occur when carbon dioxide reacts with H₂O₂ to produce a new substance.

Therefore, addition of yeast to hydrogen peroxide is a chemical change.

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Answer:

The type of change that took place is most likely a chemical change, due to the recordable reactivity of the hydrogen peroxide to the yeast granules in the experiment.

Explanation:

As stated in the question, the hydrogen peroxide started fizzing and bubbling in reaction to the yeast granules, which is already a sign of a chemical change. The question also states that there was an increase in temperature. This is another sign of a chemical change. Hope this helped (;

the coefficient of performance of this heat pump is 8.61.

The air source heat pump converts heat from the ambient air into a low-temperature liquid refrigerant. The pump compresses the liquid to raise its temperature using power. To release the heat it had been holding, it then condenses back into a liquid. Your underfloor heating system or radiators get heat.

coefficient of performance -The usable heating or cooling delivered to work (energy) needed ratio, also known as the coefficient of performance, or COP, of a heat pump, refrigerator, or air conditioning system. Higher efficiency, less energy (power) usage, and thus reduced operational costs are all related to higher COPs.

temperature of cold reservoir = -14.0°C

Tc = [ 273+ (-14.0)]K = 259K

temperature of hot reservoir = 20°C

Th = [ 273+ (20)]K = 293K

therefor, formula for coefficient of performance

Cop = Th/Th-Tc

Cop = 293/34

Cop = 8.61

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Answer:

Sodium hydroxide and water will react at room temperature. What does this indicate about its activation energy? The activation energy is at exactly 600 kJ. C. The activation energy is very low.

Explanation:

The [H3O+ ] in a solution that is initially 0. 10 m formic acid, hcooh is 0.00415M.

Formic acid is defined as the simplest carboxalic acid which contain one carbon atom. It is weak acid.

Thus we concluded from the image that the

concentration of [H30+] is 0.00413M.

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The molar mass of the other gas is 450.56 g.

Relation between rate of diffusion and molar mass of two gases is given by:

r₁/r₂ = (√m₂)/(√m₁)

Given,

r₁ = 3.2r₂                          

(r₁ is the diffusion rate of CO₂ and r₂ is the diffusion rate of the other gas)

We know

m₁ = molar mass of CO₂ = 44 g

To find,

m₂ = molar mass of the other gas =?

Put the values in the above equation,

r₁/r₂ = (√m₂)/(√m₁)

3.2r₂/r₂ = (√m₂)/(√44)

3.2 = (√m₂)/(√44)

Squaring both the sides,

10.24 = m₂/44

m₂ = 10.24 (44)

m₂ = 450.56 g

Hence, the molar mass of the other gas is 450.56 g.

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Hence the percent yield of methanol is 51.45%

Step 1: Convert Kg into g

68.5 Kg CO = 68500 g CO

8.60 Kg H₂ = 8600 g

Step 2: Find out the Limiting reactant;

The Balance Chemical Equation is as follows;

                CO + 2 H₂  →  CH₃OH

According to Equation,

         28 g (1 mol) CO reacts with = 4 g (2 mol) of H₂

So,

         68500 g CO will react with = X g of H₂

Solving for X,

          X = (68500 g × 4 g) ÷ 28 g

          X  = 9785 g of H₂

It shows that 9785 g H₂ is required to react with 68500 g of CO but we are provided with 8600 g of H₂ which is less than required. Therefore, H₂ is provided in less amount hence, it is a Limiting reagent and will control the yield of products.

Step 3: Calculate Theoretical Yield

According to the equation,

     4 g (2 mol) H₂ reacts to produce = 32 g (1 mol) Methanol

So,

            8600 g H₂ will produce = X g of CH₃OH

Solving for X,

          X  = (8600 g × 32 g) ÷ 4 g

          X = 68800 g of CH₃OH

Step 4: Calculate %age Yield

          %age Yield = Actual Yield ÷ Theoretical Yield × 100

Putting Values,

          %age Yield = 3.54 × 10⁴ g ÷ 68800 g × 100 = 51.45 %

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When 25.0 g of Mg react with 25.0 g of O₂ it produce 41.9g of MgO.

Chemical reaction:

2Mg + O₂ → 2 MgO

Given,

Mass of Mg = 24g

Mass of O₂ = 25 g

Molar mass of O₂ = 16×2

= 32 g

Molar mass of Mg = 24.3

Moles of Mg  =25/24.3

=1.04mole

Moles of O₂  =25/32

=0.78mole

From above reaction we can say that 2moles of mg react with 1moles of O₂ to give 2moles of MgO.

So, 1 mole of Mg react with 0.5 mole of O₂ to produce 1mole of MgO.

So, 1.04 react with= 0.5× 1.04

= 0.520 g oxygen to give 1.04 moles of MgO.

From above we can say that Mg is limiting reagent.

Moles of MgO =1.04

Molar mass of MgO =40.3

Mole =given mass/ molar mass

1.04  =mass/ 40.3

Mass = 1.04×40.3

41.9 g

Thus, from above we concluded that 25.0 g of Mg react with 25.0 g of O₂  it produce 41.9g of MgO.

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The correct product from this reaction is the structure in option D.

An amine is a compound that contains an alkyl group and an amino group. We know that we can obtain an amine from ammonia by replacing one or more hydrogen atoms with alkyl groups.

The compound as shown here is a secondary amine because two hydrogen atoms have been replaced with alkyl groups. We know that the reaction between the HCl and the amine produces an ionic compound owing to the fact that the nitrogen and the hydrogen from HCl are involved in a Dative bond.

As such, the correct product from this reaction is the structure in option D.

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Answer:

Hi there. In this question, we are trying to classify this reaction type. What we see happening here is we're told that we have sulfur which is in its solid state and it is reacting with solid iron And they're going to produce solid Iron three sulfide. So that is going to be f. E two S. Three. And that is a solid. I know it was F. E two S. Three because the iron three tells us the charge on the iron is three plus and sulfur voice forms ions with a too negative charge. Therefore it has to be FE two S 3. We can balance this equation although that's not necessary for this problem. But it's kind of quick. So I'll go ahead and do that. Okay, but we want to know what type of reaction it is. So we're looking for a pattern here when we see an element sulfur, it's combining with another element iron and it's producing a compound. So only one product. Alright, so looking at this general reaction type, there's only one reaction type of those five listed there, there's only one reaction type that has just one product and that is a synthesis reaction. A synthesis reaction follows this pattern where we are taking two or more simpler substances and combining them to make more complex compounds. Alright, with the simplest synthesis being element plus element equals compound. So this would be a synthesis reaction. Thank you for asking a question. And I hope this was helpful

Answer:

It should be D) Combustion Reaction