Chemistry 12

Name: __________________________

Thermochemistry Test Part I: Multiple Choice--choose the most correct answer. Place the answer on the answer sheet provided. [20] 1. What is the molar enthalpy change for the combustion of butane gas? 2 C4H10(g) + 13O2(g) 8 CO2(g) + 10H2O(g) + 5314.6 KJ A. B. C. D.

-5314.6 kJ -2657.3 kJ 2657.3 kJ 5314.6 kJ

2. Which describes the energy changes that occur when propane undergoes combustion? Type of Energy Change

Occurs as a Result of..

A.

Potential

Rearrangement of bonds

B.

Potential

An increase in molecular motion

C.

Kinetic

Rearrangement of bonds

D.

Kinetic

An increase in molecular motion

3. A 50.0 g block of copper at 10.0oC is carefully lowered into 100.0 g of water at 90.0/C in an insulated container. Which version of the first law of thermodynamics would be used to calculate the transfer of heat in this system? A. B. C. D.

mcΔTcopper = - (mc ΔTwater) mcΔTcopper = - (n ΔHwater) nΔHcopper = - (mcΔTwater) nΔHcopper = - (nΔHwater)

1

Chemistry 12

Name: __________________________

4. The graph below shows the changes in temperature of a solid as it is heated at a constant rate over a period of time:

IV I II II I

Which stage of the graph represents the energy added in order to convert the liquid form of this substance into a gas? A. B. C. D. 5.

I II III IV

What is the total amount of heat transferred by 100.0 grams of water when theo temperature of the water is increased from 30.0OC to 45.0OC? (cwater = 4.184 J/gO C) A. B. C. D.

418 J 6270 J 12 500 J 18 800 J

2

Chemistry 12

6.

Name: __________________________

Given the following: 2 C3H6(g) + 9 O2(g)  6 CO2(g) + 6 H2O(l) C(s) + O2(g)  CO2(g) H2(g) + ½ O2(g)  H2O(l)

ΔH°= –3918.4kJ ΔH°= –393.5 kJ ΔH°= –285.8 kJ

What is the molar enthalpy of formation of cyclopropane, C3H6(g)? 3 C(s) + 3H2(g)  C3H6(g), A. B. C. D. 7.

ΔH = ?

-1279.9 kJ -78.7 kJ 78.7 kJ 1279.9 kJ

A student dissolves ammonium nitrate (NH4NO3) in a fixed volume of water in a simple calorimeter. The results are shown below: Mass water

150.0g

Mass of ammonium nitrate (NH4NO3)

1.68 g

Initial temperature of calorimeter and contents

22.30 °C

Final temperature of calorimeter and contents

20.98 °C

Based on this data, what is the molar enthalpy of solution for ammonium nitrate? A. B. C. D. 8.

-39.9 kJ/mol -0.499 kJ/mol 0.499 kJ/mol 39.9 kJ/mol

What amount of water can be decomposed with the addition of 800.0 kJ of energy? 2 H2O(l) A. B. C. D.

+ 571.6 kJ  2 H2(g)

+ 1 O2(g)

6.438 g 12.88 g 50.44 g 25.22 g

3

Chemistry 12

9.

A 75.0g Chocolate Mini Roll contains 1213.4 J. How long would a student have to walk in order to burn off the energy, contained in three of these mini rolls? Activity

Energy Expenditure

Walking

810 kJ/h

A. B. C. D. 10.

12.

4.5 x 10-3 h 4.55 h 0.67 h 670 h

Which substance has a molar enthalpy of formation (ΔHf) = 0.0 kJ/mol? A. B. C. D.

11.

Name: __________________________

H2O(l) CO(l) Cl2(g) O3(g)

As a result of the reaction of a small amount of material, there is a large increase in the temperature of the water in the calorimeter. Which is true of the ΔH for the reaction? Magnitude

Sign

A.

Large

Negative

B.

Large

Positive

C.

Small

Negative

D.

Small

Positive

Which energy change occurs in water when it is heated from 25.0oC to 50.0oC? (A) KE decreases (B) KE increases (C) PE decreases (D) PE increases

4

Chemistry 12

13.

Given the molar mass and the information provided in the graph below, what additional information would be needed to calculate the energy required to heat 11.2g of the compound from point X to point Y?

(A) (B) (C) (D) 14.

Name: __________________________

ΔHfus and cliquid ΔHfus and csolid ΔHvap and cliquid ΔHvap and csolid

It was determined that adding 50.0 kJ of energy to a calorimeter causes an increase in temperature of 2.50oC. What is the energy change of a reaction, taking place in the calorimeter, if the reaction causes a temperature increase of 7.50oC? (A) (B) (C) (D)

15.

- 150 kJ - 16.7 kJ 16.7 kJ 150 kJ

What is the mass of a piece of aluminum, if it requires 3.00 kJ of energy to raise its temperature by 115oC? (Note: cAl = 0.90 J/goC) (A) (B) (C) (D)

0.029 g 29 g 310 g 3.1 x 105 g

5

Chemistry 12

Name: __________________________

16.

Place your answers to the multiple choice below: 1.

__________

9.

__________

2.

__________

10. __________

3.

__________

11. __________

4.

__________

12. __________

5.

__________

13. __________

6.

__________

14. __________

7.

__________

15. __________

8.

__________

16. __________

6

Chemistry 12

Name: __________________________

Part II: Extended Response—students must answer ALL of the following questions. [24] 1.

Calculate the amount of energy required to change 32.0 g of water at 25.0oC to steam at 100.0oC? [6] cliquid 4.184 J/goC csolid 2.01 J/goC cgas

2.01 J/goC

ΔHfu 6.02 kJ/mol s ΔHva 40.7 kJ/mol p

2.

A 2.200 g sample of quinone, C6H4O2 is burned in a bomb calorimeter that has a heat capacity of 7.854 kJ/oC. The temperature of the calorimeter and contents increased from 23.44oC to 30.57oC. Calculate the molar enthalpy of combustion for quinone. [4]

7

Chemistry 12

Name: __________________________

3.

Given the thermochemical equation: [4]

4.

5.50 g of NaOH(s) reacts with 175 mL of 0.550 mol/L HCl (aq) in a coffee cup calorimeter. If the temperature of the water increased by 2.1oC, calculate the molar enthalpy of this reaction. [4]

8

Chemistry 12

5.

Name: __________________________

Using the data below, calculate ΔH for: 2 C3H6 (g) + 9 O2 (g)

[6]

 6 CO2 (g)

+ 6 H2O (g)

Bond

Average Bond Energy (kJ/mol)

Bond

Average Bond Energy (kJ/mol)

C-C

347

O=O

498

C=C

607

C=O

745

C-H

338

O-H

460

9