CHE 111 Thermochemistry Self Quiz

You may use paper, pencil, calculator, Periodic Table, & the values given below.

Substance	Specific Heat, J/g°C	Heat of Formation, kJ/mole
Ni(s)	0.444
H2O(l)	4.18	-285.8
NH3(g)		-45.9
N2H4(g)		95.4

(Values from Handbook of Chemistry & Physics, CRC, 75th ed.)

Choose the best answer for each question below.
NOTE: If your answer has a minor difference in the last significant figure compared to an answer choice, you should choose that answer. Minor differences can arise from rounding at different points during the solution process.

Keep track of the time you spend taking this self quiz, and write this time as the response to the last question. After answering the questions, you may either "erase" them by clicking on RESET, or check yourself by clicking on SUBMIT. Both of these buttons are displayed at the end of the quiz.

Please type in your name:

1. A 21.0 g sample of nickel is heated from 21.0°C to 37.0°C. Calculate the heat exchange.

a) 149 J

b) 336 J

c) 0.00132 J

d) none of these

2. A 106 g sample of a metal at 100.0°C is added to 35.0 g of water at 24.0°C in a styrofoam coffee-cup calorimeter. The mixture is stirred and the highest temperature observed is 40.6°C. Calculate the specific heat of the metal.

a) 2.60 J/g°C

b) 0.386 J/g°C

c) 6310 J/g°C

d) none of these

3. When a 7.00 g sample of solid potassium hydroxide dissolves in 100.0 g of water in a styrofoam coffee-cup calorimeter, the temperature rises from 24.0°C to 40.1°C. Calculate  delta H for the solution process:
KOH(s)  -->  K⁺(aq)   +   OH^-(aq)

a) -7200 J

b) -53.8 kJ

c) -57.6 kJ

d) none of these

4. Magnesium oxide is produced according to this reaction:
2Mg(s)  +   O₂(g)  -->  2MgO(s)       delta H = -1203.6 kJ
Which of the following are true statements about this reaction?

a) It is endothermic, that is, heat is given off.

b) It is exothermic, that is, heat is given off.

c) It is endothermic, that is, heat is absorbed.

d) It is exothermic, that is, heat is absorbed.

e) none of these

5. Calculate delta H for this reaction:
2N₂H₄(g)   +  2H₂O(l)   -->   4NH₃(g)   +  O₂(g)

a) -946.0 kJ

b) 335.3 kJ

c) 197.2 kJ

d) none of these

6. Calculate delta H for N₂O(g)  +  NO₂(g)  -->  3NO(g) using the following data:

Rxn #		delta H, kJ
1	N2(g)  +  O2(g)   -->   2NO(g)	180.7
2	2NO2(g)   -->   2NO(g)  +  O2(g)	113.1
3	2N2(g)  +  O2(g)   -->   2N2O(g)	163.2

a) 155.6 kJ

b) 318.8 kJ

c) 457.0 kJ

d) none  of these

7. This question refers to the strategy that you used in question 6. Which of the following is a step that you need to use in solving question 6?

a) Reaction #1 was reversed.

b) Reaction #3 was reversed and multiplied by 2.

c) Reaction # 2 was divided by 2.

d) none of these

8. The heat of formation of CH₃OH(l) equals the heat of reaction of which reaction below?

a) 2C(s)  +  4H₂(g)  +  O₂(g)   -->   2CH₃OH(l)

b) CO(g)  +  2H₂(g)   -->   CH₃OH(l)

c) C(s)  +  2H₂(g)   -->  CH₃OH(l)

d) none of these

9. Which reaction types contribute to spontaneity?

a) endothermic reactions

b) exothermic reactions

c) No general relationship exists.

d) none of these

10. Which of the following is a true statement about the specific heat of a pure substance?

a) The greater the specific heat of a substance, the more exothermic are the reactions in which it participates.

b) The greater the specific heat of a substance, the higher its temperature.

c) The greater the specific heat of a substance, the greater its tendency to resist change in temperature.

d) none of these

11. Boron reacts with oxygen according to the following reaction:
4B(s)   +  3O₂(g)   -->   2B₂O₃(s)        delta H = -2509.1 kJ
Calculate the heat exchange if 24.00 g of B reacts according to this equation.

a) -1393 kJ

b) -5570 kJ

c) -1500 kJ

d) none of these

12. How many minutes did you spend taking this self quiz?