1)The change in the internal energy of a system that absorbs 2,500 J of heat and that does 7,655 J of work on the surroundings is?

  1. Does the system gain or lose heat?
  2. Is work being done on the system or by the system?
  3. Is there a net gain of energy or net lose of energy by the system?

2)When CaNCN (Hf -298 kJ) reacts with liquid water the products are calcium carbonate and ammonia gas. The complete reaction is shown below:

CaNCN + 3H2O  CaCO3 + 2NH3

  1. Calculate the heat evolved when 45 grams of liquid water is completely reacted

3)How much energy is required (in kJ) to raise 2.5 moles of liquid water from 250C to 750C?

4)Suppose a 50.0 g block of silver (specific heat = 0.2350 J/g·C) at 100C is placed in contact with a 50.0 g block of iron (specific heat = 0.4494 J/g·C) at 0C, and the two blocks are insulated from the rest of the universe. What is the final temperature of the two blocks.

5)When 80.0 grams of a certain metal at 90.0 0C was mixed with 100.0 grams of water at 30.0 0C the final equilibrium temperature of the mixture is 36.0 0C. What is the specific heat of the metal?

6)A 200-gram sample of material requires 2440 joules of heat energy to raise its temperature from 25degrees C to 85 degrees C. What is the specific heat capacity of the material?

7)If an unknown substance has cp = 0.94 J/g•C, and it loses 234500 J of energy when cooled from 207 degrees C to 101 degrees C, what is the substance’s mass?

8) Calculate the standard enthalpy of formation for the following reaction (∆Hf of C6H12 = -151.9 kJ/mol)

  1. C6H12 + 9O2 6CO2 + 6H2O

9)Answer the following questions for the reaction below:

ZnS(s) + O2(g)ZnO(s) + SO2(g)

  1. Calculate ∆H for the reaction
  2. Is the overall reaction endothermic or exothermic?
  3. Calculate the amount of heat transferred when 25 grams of Zinc Sulfide reacts at a constant pressure
  4. For a given sample of Zinc Sulfide the enthalpy of reaction is 88.8 kJ, how many grams of Sulfur Dioxide can be produced?
  5. How many kilojoules of heat are released when 45 grams of Oxygen reacts completely with Zinc Sulfide at a constant pressure?
  6. How many grams of SO2(g) are produced during an enthalpy change of -134 kJ?
  7. What is ∆H for the reverse reaction?

10) Calculate ΔH for the reaction 2 Al (s) + 3 Cl2(g)2 AlCl3(s) from the data.

2 Al (s) + 6 HCl (aq)  2 AlCl3 (aq) + 3 H2(g) / ΔH = -1049. kJ
HCl (g) HCl (aq) / ΔH = -74.8 kJ
H2(g) + Cl2(g) 2 HCl (g) / ΔH = -1845. kJ
AlCl3(s) AlCl3 (aq) / ΔH = -323. kJ

11)Calculate ΔH for the reaction CH4(g) + NH3(g)HCN (g) + 3 H2(g), given:

N2(g) + 3 H2(g) 2 NH3(g) / ΔH = -91.8 kJ
C (s) + 2 H2(g) CH4(g) / ΔH = -74.9 kJ
H2(g) + 2 C (s) + N2(g) 2 HCN (g) / ΔH = +270.3 kJ

12)Silver sulfide (Ag2S) is the common tarnish on silver objects. The reaction of

formation of silver sulfide is given below:

Ag(s) + H2S(g) + O2(g) Ag2S(s) + H2O(l)

How much Ag2S will be produced if a total of 12000 kJ of heat is transferred as a result of the reaction? The ΔHf° for H2S is -20.63 kJ/mol and the ΔHf° for Ag2S is -31.8 kJ/mol.

13) H2O(l)=>H2(g) + 1/2O2(g)

C(s) + O2(g)=>CO2(g) H=-98.4KJ

CO2(g) + 2H2O(l)=>CH4(g) + 2O2(g) H=222.6KJ

C(s) + 2H2(g)=>CH4(g) H=-18.7KJ

14) A gas expands from 267 L to 893 L at a pressure of 3.7 atm. The amount of heat required in this reaction from the surroundings is 127 J.

  1. Does the system gain or lose heat?
  2. Is this endothermic or exothermic?
  3. Is work being done on the system or by the system
  4. Is there a net gain or net loss of energy
  5. What is the change in energy for the system?

15) How much heat is absorbed when 5.53 mol of NH4NO3 solid is dissolved in water? (Hsoln = 25.7 kJ/mol) (Write the overall reaction and balance)