1. 30.0 mL of pure water at 280. K is mixed with 50.0 mL of pure water at 330. K. What is the final temperature of the mixture in kelvins?

2. What is the heat capacity of mercury if it requires 167.0 J to change the temperature of 15.0 g mercury from 25.0°C to 33.0°C?

3. A 140.0-g sample of water at 25.0°C is mixed with 100.0 g of a certain metal at 100.0°C. After thermal equilibrium is established, the (final) temperature of the mixture is 29.6¯C. What is the heat capacity of the metal, assuming it is constant over the temperature range concerned?

4. Consider the reaction C₂H₅OH_(l) + 3O₂(g) ----> 2CO_2(g) +3H₂O_(l), DH = -1.37 x 10³ kJ

When a 15.1-g sample of ethyl alcohol (molar mass = 46.1 g/mol) is burned, how much energy is released as heat?

5. The total volume of hydrogen gas needed to fill the Hindenburg was 2.00 x 10⁸L at 1.00 atm and 25.0°C. How many kilojoules of energy were evolved when it burned?

H_2(g) + (1/2)O_2(g) ---> H₂O_(l), D H = -286 kJ

6. A bomb calorimeter has a heat capacity of 2.47 kJ/K. When a 0.105 g sample of ethylene (C₂H₄) is combusted in this calorimeter, the temperature increases by 2.14 K. What is the energy of combustion for one mole of ethylene?

7. Using Hess's Law and equations 1-3 below, find D H at 25*C for the oxidation of C₂H₅OH_(l)

C₂H₅OH_(l) + 3O_2(g) ---> 3H₂O_(l) + 2CO_2(g)

1. C₂H_4(g) + 3O_2(g) ---> 2CO_2(g)+ 2H₂O_(l) D H = -1411 kJ

2. C_(graphite) + 3H_2(g) + (1/2)O_2(g) ---> C₂H₅OH_(l) D H = -278 kJ

3. C₂H_4(g) + H₂O_(l) ---> C₂H₅OH_(l) D H = -44 kJ

8. A 58.5 g sample of a metal at 95.0 C with a specific heat capacity of 0.576J/gc is placed into 150.0 g of water at 25 C. What is the final temperature of the metal?

9. Calculate D H for the reaction C₄H_4(g) + 2H_2(g) ---> C₄H_8(g) , using the following data:

D H combustion for C₄H₄(g) = -2341 kJ/mol

D H combustion for H₂(g) = -286 kJ/mol

D H combustion for C₄H₈(g) = -2755 kJ/mol

10. The combustion of methanol takes place according to the reaction:

2CH₃OH_(l) + 3O_2(g) ---> 2CO_2(g) + 4H₂O_(l)

Compute D H for the combustion of one mole of methanol under standard conditions, given the following standard heats of formation:

D H for CH₃OH_(l) = -238.5 kJ/mol

D H for CO₂(g) = -393.5 kJ/mol

D H for H₂O_(l) = -285.6 kJ/mol

 11. Be able to draw and label energy profiles of an exothermic and endothermic reaction.

Answers:

1) 311K

2) 1.39 J/gc

3) .382/gc

4) 449kJ

5) 2.34x10⁶kJ

6) 1410kJ

7) D H = -1367kJ

8) 28.7 °C

9) D H = -158kJ

10) -726.2kJ/mol