Chemistry: Thermodynamics
Which of the following is an example of an
exothermic phase change? - ANSWER: . water vapor condensing from the air on a cold
window
You have two water samples. Sample X has a volume of 750 mL and a temperature of
42◦C. Sample Y has a volume of 380 mL and a temperature of 42◦C. Which sample
contains the most heat? - ANSWER: Sample X
Which of the following processes is endothermic; i.e., requires addition of heat to occur?
- ANSWER: melting (solid → liquid)
Calculate the standard reaction enthalpy for the reaction of calcite with hydrochloric acid
CaCO3(s) + 2 HCl(aq) −→ CaCl2(aq) + H2O(ℓ) + CO2(g) The standard enthalpies of
formation are:
for CaCl2(aq) : −877.1 kJ/mol;
for H2O(ℓ) : −285.83 kJ/mol;
for CO2(g) : −393.51 kJ/mol;
for CaCO3(s) : −1206.9 kJ/mol;
and for HCl(aq) : −167.16 kJ/mol. - ANSWER: −15.2 kJ/mol
3.5 g of a hydrocarbon fuel is burned in a vessel that contains 250. grams of water
initially at 25.00 C. After the combustion, the temperature of the water is 26.55 C. How
much heat is evolved per gram of fuel burned? - ANSWER: 463 J/g
If 8000 calories of heat are added to 200 g of water at 20◦C, what is the final
temperature of the water? - ANSWER: 60◦C
A calorimeter... - ANSWER: is a device used to measure the transfer of heat energy.
Carbon monoxide reacts with oxygen to form carbon dioxide by the following reaction: 2
CO(g) + O2(g) → 2 CO2(g) ∆H for this reaction is −135.28 kcal. How much heat would
be released if 12.0 moles of carbon monoxide reacted with sufficient oxygen to produce
carbon dioxide? - ANSWER: . 811.68 kcal
Calculate the standard enthalpy of combustion of ethanol at 298 K from standard
enthalpy of formation data. - ANSWER: −1367 kJ · mol−1
A sample of 1.67 grams of Z is dissolved into 500 grams of water which is in a
styrofoam coffee cup. The temperature is monitored and is found to rise from 25.594◦C
to 26.041◦C. What is ∆Hsolution for substance Z? Assume no heat is lost/gained by the
Which of the following is an example of an
exothermic phase change? - ANSWER: . water vapor condensing from the air on a cold
window
You have two water samples. Sample X has a volume of 750 mL and a temperature of
42◦C. Sample Y has a volume of 380 mL and a temperature of 42◦C. Which sample
contains the most heat? - ANSWER: Sample X
Which of the following processes is endothermic; i.e., requires addition of heat to occur?
- ANSWER: melting (solid → liquid)
Calculate the standard reaction enthalpy for the reaction of calcite with hydrochloric acid
CaCO3(s) + 2 HCl(aq) −→ CaCl2(aq) + H2O(ℓ) + CO2(g) The standard enthalpies of
formation are:
for CaCl2(aq) : −877.1 kJ/mol;
for H2O(ℓ) : −285.83 kJ/mol;
for CO2(g) : −393.51 kJ/mol;
for CaCO3(s) : −1206.9 kJ/mol;
and for HCl(aq) : −167.16 kJ/mol. - ANSWER: −15.2 kJ/mol
3.5 g of a hydrocarbon fuel is burned in a vessel that contains 250. grams of water
initially at 25.00 C. After the combustion, the temperature of the water is 26.55 C. How
much heat is evolved per gram of fuel burned? - ANSWER: 463 J/g
If 8000 calories of heat are added to 200 g of water at 20◦C, what is the final
temperature of the water? - ANSWER: 60◦C
A calorimeter... - ANSWER: is a device used to measure the transfer of heat energy.
Carbon monoxide reacts with oxygen to form carbon dioxide by the following reaction: 2
CO(g) + O2(g) → 2 CO2(g) ∆H for this reaction is −135.28 kcal. How much heat would
be released if 12.0 moles of carbon monoxide reacted with sufficient oxygen to produce
carbon dioxide? - ANSWER: . 811.68 kcal
Calculate the standard enthalpy of combustion of ethanol at 298 K from standard
enthalpy of formation data. - ANSWER: −1367 kJ · mol−1
A sample of 1.67 grams of Z is dissolved into 500 grams of water which is in a
styrofoam coffee cup. The temperature is monitored and is found to rise from 25.594◦C
to 26.041◦C. What is ∆Hsolution for substance Z? Assume no heat is lost/gained by the
