CHEM101 Lecture Notes - Lecture 10: State Function, Exothermic Process, Enthalpy

1.According to the following thermochemical equation, if 31.1 g of NO2 is produced, how much heat is released at constant pressure?how much heat is released at constant pressure?

2NO(g) + O2(g) → 2NO2(g);ΔH° = –114.4 kJ

Select one:

a. 114.4 kJ114.4 kJ

b. 1.183×103kJ

c. 2.365×103kJ

d. 38.7 kJ

e. 1.088×105kJ

2.Calculate   ΔU   of a gas for a process in which the gas absorbs   12 J   of heat and does   20 J   of work by expanding.

Select one:

a. 8 J

b. 32 J

c. -32 J

d. 0, because  ΔU is a state function

e. -8 J

3.If q = +56 kJ for a certain process, that process

Select one:

a. requires a catalyst.

b. is exothermic.

c. occurs rapidly.

d. is endothermic.

e. cannot occur.

4.If q = 18 kJ and w = 15 kJ for a certain process, that process

Select one:

a. requires a catalyst.

b. has an increase in internal energy.

c. occurs slowly.

d. is exothermic.

e. cannot occur.

5.What is the change in internal energy of the system (ΔU) if 10 kJ of heat energy is released by the system and  70 kJ  of work is done on the system for a certain process?

Select one:

a. –60 kJ

b. 80 kJ

c. 10 kJ

d. 60 kJ

e. −80 kJ

6.What is the quantity of heat evolved at constant pressure when   26.3 g   H2O(l)   is formed from the combustion of H2(g) and O2(g)?

2H2(g) + O2(g) → 2H2O(l);ΔH° = –571.6 kJ

Select one:

a. 15033 kJ

b. 15.03 kJ

c. 1.72×104 kJ

d. 417.6 kJ

e. 9.57×102 kJ

7.What quantity, in moles, of hydrogen is consumed when 76.8 kJ of energy is evolved from the combustion of a mixture of H2(g) and O2(g)?

H2(g) + O2(g) →2H2O(l);ΔH° = –571.6 kJ

Select one:

a. 2.368 mol

b. 1.184 mol

c. 0.4223 mol

d. 0.2687 mol

e. 1.368 mol

8. Which of the following is an exothermic process?

Select one:

a. work is done by the system on the surroundings

b. heat energy flows from the system to the surroundings

c. work is done on the system by the surroundings

d. heat energy is absorbed by the system

e. none of the above

9. Which of the following statements is correct?

Select one:

a. Internal energy is not a state function.

b. The value of q is negative when heat flows into a system from the surroundings.

c. The value of q is negative in an endothermic process.

d. Heat flows from a system into the surroundings in an exothermic process.

e. Enthalpy is not a state function.

10.X2and F2react according to the following equation, forming XF. (X is an unknown diatomic element)

X2(g)+ F2(g)→2XF(g);ΔH°=+271 kJ

If X2(g) and F2(g) were mixed in a thermally insulated vessel, the reaction that occurred would be

Select one:

a. endothermic, and the temperature of the reaction system would fall.

b. We could not tell unless the original and final temperatures were given.

c. exothermic, and the temperature of the reaction system would fall.

d. exothermic, and the temperature of the reaction system would rise.

e. endothermic, and the temperature of the reaction system would rise.