15 Questions

Chapter 17 THERMOCHEMISTRY

Questions and Answers

- 1.The SI unit of energy is
- A.
Heat capacity.

- B.
Calorie.

- C.
Joule.

- D.
Enthalpy.

- 2.How many calories are required to raise the temperature of 75.0 g of water from 20C to 50C?
- A.
2250 cal

- B.
3750 cal

- C.
75.0 cal

- 3.If 1 Calorie 4.18 kJ, how many kJ of energy can be released by an apple containing 125 Cal?
- A.
522 kJ

- B.
29.9 kJ

- C.
5.22 105 kJ

- 4.The temperature of a 6.0-g sample of glass changed from 20C to 45C when it absorbed 550 J of heat. What is the specific heat of this glass sample?
- A.
C0.27 J/gpC

- B.
3.7 J/gp

- C.
2300 J/gpC

- 5.The enthalpy of a system is the same as its:
- A.
Specific heat.

- B.
Heat of combustion.

- C.
Heat content.

- 6.When your body is warmed by an electric blanket during the winter, this process is said to be
- A.
Endothermic.

- B.
Exothermic.

- C.
Isothermic.

- 7.
- A.
325 kJ

- B.
272 kJ

- C.
1.36 kJ

- 8.Given the equation 2Mg(
*s*) O2(*g*) y2MgO(*s*) 72.3 kJ, which of the following is true?- A.
The reaction is endothermic.

- B.
^H72.3 kJ

- C.
^H72.3 kJ

- 9.Given the equation in question 18, how much heat is involved in the production of 5.0 mol of MgO?
- A.
72 kJ

- B.
360 kJ

- C.
180 kJ

- 10.Given the equation Si(
*s*) + 2Cl2(*g*) ------>SiCl2(*g*) ------>SiCl2(*l*) + 687 kJ, how much heat is produced when 106 g of Cl2 react?- A.
513 kJ

- B.
360 kJ

- C.
180 kJ

- 11.Which of the following statements is true?
- A.
^Hfus^Hsolid

- B.
^Hfus^Hsolid

- C.
^Hsolid is always positive.

- 12.How much heat, in kJ, is required to melt 54.0 g of ice at 0C into water at 0C if ^
*H*fus for water = 6.01 kJ/mol?- A.
0.111 kJ

- B.
325 kJ

- C.
18.0 kJ

- 13.How much heat is required to convert 9.00 g of water at 100C into steam at 100C, if ^
*H*vap for water = 40.7 kJ/mol?- A.
20.4 kJ

- B.
366 kJ

- C.
18.0 kJ

- 14.If the molar heat of solution of NH4NO3 is 25.7 kJ/mol, how much heat (in kJ) would be required to dissolve 20.0 g of NH4NO3 in water?
- A.
0.250 kJ

- B.
514 kJ

- C.
6.43 kJ

- 15.
- A.
291.9 kJ

- B.
+291.9 kJ

- C.
279.9 k