Answers
The researcher initially added approximately 13 g of KF to the water.
How do you calculate the unknown mass of KF in water?First, you calculate the amount of heat absorbed by the water when the KF dissolves.
We can use the equation:
q = mCΔT
where q is the amount of heat absorbedm is the mass of waterC is the specific heat capacity of waterΔT is the change in temperature.We can assume that the KF has a negligible heat capacity and does not contribute to the heat absorption.
Using the given values, we have:
q = mCΔT
q = (238 g - mKf)(4.184 J/g·°C)(31.51°C - 18.98°C)
q = (238 g - mKf)(86.05 J/g)
Next, we can use the fact that the amount of KF added is equal to the amount of KF dissolved in the water.
We can also assume that the KF fully dissociates into K+ and F- ions when it dissolves:
KF(s) → K+(aq) + F-(aq)
Therefore, the moles of K+ ions are equal to the moles of KF added to the water.
We can use the following equation to calculate the moles of K+ ions:
moles K+ = mass KF / molar mass KF
where the molar mass of KF is 58.10 g/mol.
Since the solution is electrically neutral, the moles of F- ions are also equal to the moles of KF added.
Next, we can use the following equation to calculate the concentration of the ions in the solution:
C = moles / volume
Assuming that the volume of the solution is equal to the mass of the solution (since the density of water is close to 1 g/mL), we have:
C K+ = moles K+ / (238 g - mKf)
C F- = moles F- / (238 g - mKf)
Finally, we can use the fact that KF is a strong electrolyte and dissociates completely in water to write the following equation for the heat absorbed during the dissolution:
q = (moles K+) ΔHfus + (moles K+)ΔHsol + (moles F-)ΔHsol
where ΔHfus is the heat of fusion of KFΔHsol is the heat of solution of KF.The heat of fusion of KF is 10.8 kJ/mol, and the heat of solution is -155.2 kJ/mol.
Substituting all the equations and values above, we get:
(238 g - mKf)(4.184 J/g·°C)(31.51°C - 18.98°C) =
((mKf / 58.10 g/mol) ΔHfus + (mKf / 58.10 g/mol)ΔHsol + (mKf / 58.10 g/mol)ΔHsol) + ((238 g - mKf) (mKf / 58.10 g/mol) (-155.2 kJ/mol))
Simplifying this equation gives:
mKf ≈ 13 g
Therefore, the researcher initially added approximately 13 g of KF to the water.
Learn more about unknown mass of salts in water at:
https://brainly.com/question/7053858
#SPJ1
Related Questions
HELP NEEDED ASAP THANK YOU SO MUCH!!
For the reaction C + 2H2 - CH4
how many grams of carbon are required to produce 10.7 moles of methane, CH4?
Use the following molar masses:
hydrogen: 1
carbon: 12
Answers
The balanced chemical equation for the reaction C + 2H2 → CH4 tells us that one mole of carbon produces one mole of methane. So, if 10.7 moles of methane are produced, then 10.7 moles of carbon are required to produce it.
To find the mass of carbon required to produce 10.7 moles of methane, we can use the molar mass of carbon (12 g/mol) and the following calculation:
Mass of carbon = Number of moles of carbon × Molar mass of carbon
Mass of carbon = 10.7 mol × 12 g/mol
Mass of carbon = 128.4 g
Therefore, 128.4 grams of carbon are required to produce 10.7 moles of methane, CH4.
Answer:
128.40g
Explanation:
Grams of carbon = moles of carbon * molar mass of carbon
Grams of carbon = 10.7 moles * 12 g/mol
HELP NEEDED ASAP THANK YOU SO MUCH!!
For the reaction C + 2H2 - CH4
how many grams of carbon are required to produce 10.7 moles of methane, CH4?
Use the following molar masses:
hydrogen: 1
carbon: 12
Answers
128.4 grams of carbon are required to produce 10.7 moles of methane.
The balanced chemical equation for the reaction C + 2H2 - CH4 is as follows:C + 2H2 ⟶ CH4.
In this equation, we can see that for one mole of methane (CH4), one mole of carbon (C) and two moles of hydrogen (H2) are required.
The molar mass of carbon is 12 g/mol.
The molar mass of methane is the sum of the molar masses of its constituent atoms, which is 12 g/mol (for carbon) + 4(1 g/mol) (for hydrogen) = 16 g/mol.
To find the amount of carbon required to produce 10.7 moles of methane, we can use the following proportion:1 mole CH4 : 1 mole C
Therefore,10.7 moles CH4 : x moles C.
Thus,x = 10.7 moles C.
Since we know the molar mass of carbon (12 g/mol), we can convert the moles of carbon to grams:mass = moles × molar massmass of carbon required = 10.7 moles × 12 g/mol= 128.4 g.
For more such questions on methane
https://brainly.com/question/28723437
#SPJ8
2) Make Flash cards elaborating following terms with example: i. Mole ii. Compounds iii. Molecular Mass iv. Types of Mixture v. Free Radical vi. Gram formula mass
Answers
(i) A mole is the amount of a substance containing 6.022 × 10²³ particles.
(ii) Compounds are formed by the chemical bonding of different elements.
(iii) Molecular mass is the sum of atomic masses in a molecule.
(iv) There are two types of mix homogeneous and heterogeneous mixtures.
(v) Free radicals are highly reactive species with unpaired electrons.
(vi) Gram formula mass is the sum of atomic masses expressed in grams per mole.
(i) Mole: A mole is defined as the quantity of a substance that has an equal number of particles that are in 12 grams of carbon-12.
It is denoted by mol and is used in chemistry to measure quantities of atoms or molecules.
Example:1 mol of oxygen gas contains 6.022 × 10²³ oxygen molecules.
(ii) Compounds: Compounds are substances made up of two or more different elements that are chemically bonded together.
They can be broken down into simpler substances through chemical reactions.
Example:Water (H2O) is a compound made up of two hydrogen atoms and one oxygen atom that are chemically bonded together.
(iii) Molecular Mass: The molecular mass of a compound is the sum of the atomic masses of all the atoms in the molecule.
It is expressed in atomic mass units (amu) or grams per mole.
Example:The molecular mass of water (H2O) is 18.015 amu.
(iv) Types of Mixture: A mixture is a combination of two or more substances that are not chemically combined.
There are two types of mixtures - homogeneous and heterogeneous.
Example:A homogeneous mixture is a solution, such as saltwater, where the solute (salt) is evenly distributed in the solvent (water).
A heterogeneous mixture is a mixture that is not evenly distributed, such as oil and water.
(v) Free Radical: A free radical is an atom or molecule that has an unpaired electron in its outer shell and is highly reactive. They can be both harmful and helpful to the human body.
Example:A common free radical is the hydroxyl radical (OH·) that is formed by the body during metabolism.
(vi) Gram formula mass: The gram formula mass is the sum of the atomic masses of all the atoms in a compound.
It is expressed in grams per mole and is used to determine the mass of a certain number of molecules or atoms.
Example:The gram formula mass of water (H2O) is 18.015 g/mol.
For more such questions on homogeneous
https://brainly.com/question/14441492
#SPJ8
PLEASE HELP ASAP!
5 + 6 HNO3 -> H2504 + 6 NO2 + 2H20
In the above equation how many moles of water can be made when 112.6 grams of HNO3 are consumed?
Use the following molar masses. If you do not use these masses, the computer will mark your answer incorrect.:
Hydrogen 1
Nitrogen 14
Sulfur 32
Oxygen 16
Answers
0.595 moles of water can be made at 112.6 grams of [tex]HNO_{3}[/tex] are consumed
To determine the number of moles of water produced when 112.6 grams of [tex]HNO_{3}[/tex] are consumed, we use the equation's stoichiometry and molar masses.
To determine the number of moles of water produced when 112.6 grams of [tex]HNO_{3}[/tex] are consumed, we need to use the molar mass of [tex]HNO_{3}[/tex] and the stoichiometric coefficients of the balanced chemical equation.
The molar mass of [tex]HNO_{3}[/tex] is calculated as follows:
1 mole of hydrogen (H) = 1 g/mol
1 mole of nitrogen (N) = 14 g/mol
3 moles of oxygen (O) = 3 × 16 g/mol = 48 g/mol
Adding these together, the molar mass of [tex]HNO_{3}[/tex] is 1 + 14 + 48 = 63 g/mol.
Now, we can set up a conversion factor using the stoichiometry of the balanced equation:
From the equation: 5 + 6 [tex]HNO_{3}[/tex] -> [tex]H_{2}SO_{4}[/tex] + 6 [tex]NO_{2}[/tex] + 2 [tex]H_{2}O[/tex]
From the coefficients: 6 moles of [tex]HNO_{3}[/tex] produce 2 moles of [tex]H_{2}O[/tex]
To find the moles of water produced, we use the following calculation:
112.6 g [tex]HNO_{3}[/tex] × (1 mol [tex]H_{2}O[/tex] / 63 g [tex]HNO_{3}[/tex]) × (2 mol [tex]H_{2}O[/tex] / 6 mol [tex]HNO_{3}[/tex]) = 0.595 mol [tex]H_{2}O[/tex]
Therefore, when 112.6 grams of [tex]HNO_{3}[/tex] are consumed, approximately 0.595 moles of water can be produced according to the given balanced equation and molar masses.
Know more about molar mass here:
https://brainly.com/question/837939
#SPJ8
How do you explain moles with the help of boxes and apples?
Answers
Answer:
See explanation
Explanation:
A mole is a counting unit, which means that it is like a dozen, or a pair, except that instead of having 12 or 2 of something, there are 6.022*10^23 of them. Why do chemists use moles instead of the number of atoms? That is where the boxes and apples come in. Lets say a company has 13340 apples, which is a lot. The company sends out and receives their apples in boxes of 667 apples. No one wants to say "we have thirteen thousand, three hundred and four hundred apples in stock right now." Instead, they all say "We just got twenty boxes of apples". You can see how the company doesn't like dealing with large numbers, so they use boxes to simplify apple counting. Chemists are the same. No one wants to say "Here, have six hundred two sextillion two hundred fourteen quintillion seventy-six quadrillion glucose molecules", instead, we/they say "Here, have a mole of glucose."
A student sets up the following equation to convert a measurement fill in the missing part of this equation(0.050 ug/dL)• [] = ? g/mL
Answers
Answer:
To convert a measurement of 0.050 ug/dL to g/mL, we need to multiply it by a conversion factor that relates micrograms (ug) to grams (g) and deciliters (dL) to milliliters (mL).
1 ug = 0.000001 g (or 1 g = 1,000,000 ug)
1 dL = 100 mL
So, the missing part of the equation would be:
(0.050 ug/dL) • (0.000001 g/ug) • (1 dL/100 mL) = 0.0000000005 g/mL
Therefore, the answer is 0.0000000005 g/mL.
Explanation:
