Thermochemistry

A system that does no work but which receives heat from the surroundings has
1. q<0, U>0
2. q>0, U<0
3. q = U
4. q = -U
A system which undergoes an adiabatic change and has work done on it by the surroundings has
1. w = U
2. w = -U
3. w>0, U<0
4. w<0, U>0
A system delivers 225J of heat to the surroundings while delivering 645J of work. Calculate the change in the internal energy, U, of the system.
1. -420 J
2. 420 J
3. -870 J
4. 870 J
A system absorbs 21.6 kJ of heat while performing 6.95 kcal of work on the surroundings. Calculate the change in the internal energy, U, of the system.
1. -7.5 kcal
2. -1.79 kcal
3. 12.11 kcal
4. 28.6 kcal
In which of the following processes is H = U?
1. Two moles of ammonia gas are cooled from 325^oC to 300^oC at 1.2 atm.
2. One gram of water is vaporized at 100^oC and 1 atm.
3. Two moles of hydrogen iodide gas react to form hydrogen gas and iodine gas in a 40-L container.
4. Calcium carbonate is heated to form calcium oxide and carbon dioxide in a container with variable volume.
Which of the following is not a state function?
1. internal energy
2. volume
3. work
4. pressure
A Snickers® candy bar with a mass of 58.7 g contains 14 g of fat. The fat accounts for 120 of the 280 Calories (kcal) in the candy bar. How much energy is contained in the 14 g of fat in the Snickers® bar?
1. 29 kJ
2. 5.0 x 10² kJ
3. 2.9 x 10⁴ kJ
4. 3.5 x 10⁵ kJ
If, as a pioneer, you wished to warm your room by taking an object heated on top of a pot-bellied stove to it, which of the following 15-pound objects would be the best choice? The specific heat capacity (in J/gK) for each substance is given in parentheses. Iron (0.450), copper (0.387), granite (0.79), or gold (0.129)
1. iron
2. copper
3. granite
4. gold
A 275 g sample of nickel at 100.0^oC is placed in 100.0 mL of water at 22.0^oC. What is the final temperature of the water? Assume that no heat is lost to or gained from the surroundings. Specific heat capacity of nickel = 0.444 J/gK
1. -10.1^oC
2. 39.7 ^oC
3. 64.9^oC
4. 72.1^oC
When Karl Kaveman adds chilled grog to his new granite mug, he removes 10.9 kJ of energy from the mug. If it has a mass of 625 g and was at 25^oC, what is its new temperature? Specific heat capacity of granite = 0.79 J/gK
1. 3^oC
2. 14^oC
3. 22^oC
4. 47^oC
A common laboratory reaction is the neutralization of an acid with a base. When 50.0 mL of 0.500 M HCl at 25.0^oC is added to 50.0 mL of 0.500 M NaOH at 25.0^oC in a coffee cup calorimeter, the temperature of the mixture rises to 28.2^oC. What is the heat of reaction per mole of acid?
1. 675 J
2. 1350 J
3. 27.0 kJ
4. 54.0 kJ
Calcium hydroxide, which reacts with carbon dioxide to form calcium carbonate, was used by the ancient Romans as mortar in stone structures. The reaction for this process is
Ca(OH)_2(s) + CO_2(g) CaCO_3(s) + H₂O_(g) H = -69.1 kJ
What is the enthalpy change if 3.8 mol of calcium carbonate is formed?
1. -18 kJ
2. -69 kJ
3. -73 kJ
4. -260 kJ
The highly exothermic thermite reaction, in which aluminum reduces iron(III) oxide to elemental iron, has been used by railroad repair crews to weld rails together.
2Al_(s) + Fe₂O_3(s) 2Fe_(s) + Al₂O_3(s) H = -850 kJ
What mass of iron is formed when 725 kJ of heat are released?
1. 47 g
2. 65 g
3. 95 g
4. 130 g
Calculate the enthalpy change for the reactions
NO_(g) + O_(g) NO_2(g)
from the following reactions:
NO_(g) + O_3(g) NO_2(g) + O_2(g) H = -198.9 kJ
O_3(g) 1.5O_2(g) H = -142.3 kJ
O_2(g) 2O_(g) H = 495.0 kJ
1. -551.6 kJ
2. -304.1 kJ
3. 153.8 kJ
4. 438.4 kJ
Calculate the H^o_rxn for the decomposition of calcium carbonate to calcium oxide and carbon dioxide. H^o_f(CaCO_3(s)) = -1206.9 kJ/mol; H^o_f(CaO_(s)) = -635.1 kJ/mol; H^o_f(CO_2(g)) = -393.5 kJ/mol
CaCO_3(s) CaO_(s) + CO_2(g)
1. -2235.5 kJ
2. -178.3 kJ
3. 178.3 kJ
4. 2235.5 kJ

Thermochemistry

Quiz