CHE 114 - FINAL EXAM QUESTIONS AND ANSWERS
100% VERIFIED
Colligative properties are dependent on
_______________ a solute, but are not dependent on
_______________ of the solute - ANSWER 1. the amount of
2. the nature of
1. vapor pressure lowering
2. boiling point elevation
3. freezing point depression
4. color
5. density - ANSWER 1. colligative
2. colligative
3. colligative
4. non-colligative
5. non-colligative
Solutions are comprised of two parts; a solvent and a solute.
The _________ is the substance that dissolves and is present in a ___________ amount in the
solution. The ____________ is the medium for dissolving and is present in a ___________ amount in
,the solution. - ANSWER 1. Solute
2. Smaller
3. Solvent
4. Larger
Molality can be expressed as the - ANSWER (moles of solute)/(kg solvent)
Ethyl propanoate is an organic molecule that smells like pineapple and has a molar mass of
102.132 g/mol. It is soluble in the organic solvent acetone.
What is the molality of a solution prepared with 21.9 g of ethyl propanoate and 744.8 mL of
acetone? The density of acetone is 0.784 g/mL. - ANSWER Molality = moles of
solute/kilograms of solvent
21.9 g ethyl propanoate x (1 mol ethyl propanoate)/(102.132 g ethyl propanoate) = 0.2144
solvent mass in kg = 744.8 mL acetone x (0.784 g acetone)/(1 mL acetone) x (0.001 kg)/(1 g) =
0.58393
0.2144/0.58393 = 0.3672 (ANS)
At the freezing point, the liquid form of a substance _____________________________ the solid form
of the substance. - ANSWER 1. Is in equilibrium with
,Identify the variables or units in the freezing point depression equation.
________ (ºC) = Kf ________ x i x ________ (mol/kg) - ANSWER 1. ΔT
2. (ºC/m)
3. m
ΔTf is the change in freezing point with units of ºC,
Kf is molal freezing point depression constant with units of ºC/m,
i is the van't Hoff factor,
m is molality with units of mol/kg
Suppose you are measuring the freezing point depression due to the presence of a
non-electrolyte in solution using the equation
ΔTf=iKfm
Which value in the equation do you know because the solute is a non-electrolyte?
1. ΔTf
2. i
3. Kf
, 4. m - ANSWER 2. i
What is the freezing point (in degrees Celcius) of 4.21 kg of water if it contains 210.4 g of
butanol, C4H9OHC4H9OH?
The freezing point depression constant for water is 1.86 oC/m and the molar mass of butanol
is 74.12 g/mol. - ANSWER m = [(210.4g x (1/74.12)]/4.21 = 0.674
ΔTf = 1 x 1.86ºC/m x m = 1.25
0 - 1.25 = -1.25 (ANS)
Students are investigating a solvent for use in freezing point depression experiments. They
measured the freezing point of the solvent as −12.6 ⁰C. The solution they made by dissolving
0.484 g of the non-electrolyte ethanol (46.07 g/mol) in 8.254 g of the solvent has a freezing
point of -18.3 ⁰C.
Determine the freezing point depression constant, Kf, for the solvent. - ANSWER ΔTf=iKfm
Mass/molar Mass= 0.484g/46.07 g/moll = 0.0105 mol
Mass of solvent = 8.254g or 0.00825 kg
100% VERIFIED
Colligative properties are dependent on
_______________ a solute, but are not dependent on
_______________ of the solute - ANSWER 1. the amount of
2. the nature of
1. vapor pressure lowering
2. boiling point elevation
3. freezing point depression
4. color
5. density - ANSWER 1. colligative
2. colligative
3. colligative
4. non-colligative
5. non-colligative
Solutions are comprised of two parts; a solvent and a solute.
The _________ is the substance that dissolves and is present in a ___________ amount in the
solution. The ____________ is the medium for dissolving and is present in a ___________ amount in
,the solution. - ANSWER 1. Solute
2. Smaller
3. Solvent
4. Larger
Molality can be expressed as the - ANSWER (moles of solute)/(kg solvent)
Ethyl propanoate is an organic molecule that smells like pineapple and has a molar mass of
102.132 g/mol. It is soluble in the organic solvent acetone.
What is the molality of a solution prepared with 21.9 g of ethyl propanoate and 744.8 mL of
acetone? The density of acetone is 0.784 g/mL. - ANSWER Molality = moles of
solute/kilograms of solvent
21.9 g ethyl propanoate x (1 mol ethyl propanoate)/(102.132 g ethyl propanoate) = 0.2144
solvent mass in kg = 744.8 mL acetone x (0.784 g acetone)/(1 mL acetone) x (0.001 kg)/(1 g) =
0.58393
0.2144/0.58393 = 0.3672 (ANS)
At the freezing point, the liquid form of a substance _____________________________ the solid form
of the substance. - ANSWER 1. Is in equilibrium with
,Identify the variables or units in the freezing point depression equation.
________ (ºC) = Kf ________ x i x ________ (mol/kg) - ANSWER 1. ΔT
2. (ºC/m)
3. m
ΔTf is the change in freezing point with units of ºC,
Kf is molal freezing point depression constant with units of ºC/m,
i is the van't Hoff factor,
m is molality with units of mol/kg
Suppose you are measuring the freezing point depression due to the presence of a
non-electrolyte in solution using the equation
ΔTf=iKfm
Which value in the equation do you know because the solute is a non-electrolyte?
1. ΔTf
2. i
3. Kf
, 4. m - ANSWER 2. i
What is the freezing point (in degrees Celcius) of 4.21 kg of water if it contains 210.4 g of
butanol, C4H9OHC4H9OH?
The freezing point depression constant for water is 1.86 oC/m and the molar mass of butanol
is 74.12 g/mol. - ANSWER m = [(210.4g x (1/74.12)]/4.21 = 0.674
ΔTf = 1 x 1.86ºC/m x m = 1.25
0 - 1.25 = -1.25 (ANS)
Students are investigating a solvent for use in freezing point depression experiments. They
measured the freezing point of the solvent as −12.6 ⁰C. The solution they made by dissolving
0.484 g of the non-electrolyte ethanol (46.07 g/mol) in 8.254 g of the solvent has a freezing
point of -18.3 ⁰C.
Determine the freezing point depression constant, Kf, for the solvent. - ANSWER ΔTf=iKfm
Mass/molar Mass= 0.484g/46.07 g/moll = 0.0105 mol
Mass of solvent = 8.254g or 0.00825 kg
