# Solving various thermodynamics questions

1 - The air in an inflated balloon (defined as the system) is warmed over a toaster and absorbs 130J of heat. As it expands, it does 76kJ of work. What is the change in internal energy for the system?

2 - A piston has an external pressure of 8.00 atm. How much work has been done in joules if the cylinder goes from a volume of 0.140 liters to 0.450 liters.

3 - A volume of 105mL of H2O is initially at room temperature (22.0∘C). A chilled steel rod at 2.00∘C is placed in the water. If the final temperature of the system is 21.3∘C, what is the mass of the steel bar?

Use the following values:

specific heat of water = 4.18 J/(g∘C)

specific heat of steel = 0.452 J/(g∘C)

4 - The specific heat of water is 4.18 J/(g∘C). Calculate the molar heat capacity of water.

5 - It takes 47.0J to raise the temperature of an 11.3g piece of unknown metal from 13.0∘C to 24.1∘C. What is the specific heat for the metal?

6 - The molar heat capacity of silver is 25.35 J/mol∘C . How much energy would it take to raise the temperature of 11.3g of silver by 19.0∘C ?

7 - What is the specific heat of silver?

8 - If this expansion occurs against an external pressure of 1.0 atm, how much work (in J ) is done during the expansion?

9 - A gas is compressed from an initial volume of 5.40L to a final volume of 1.20L by an external pressure of 1.00 atm . During the compression the gas releases 128J of heat.

What is the change in internal energy of the gas?

10 - A mole of X reacts at a constant pressure of 43.0 atm via the reaction

X(g)+4Y(g)→2Z(g), ΔH ∘ =−75.0 kJ

Before the reaction, the volume of the gaseous mixture was 5.00 L . After the reaction, the volume was 2.00 L . Calculate the value of the total energy change, ΔE , in kilojoules.

11 - The change in internal energy for the combustion of 1.0 mol of octane at a pressure of 1.0 atm is 5084.2kJ .If the change in enthalpy is 5074.4kJ how much work is done during the combustion?

12 - What mass of natural gas (CH 4 ) must you burn to emit 267kJ of heat?

CH 4 (g)+2O 2 (g)→CO 2 (g)+2H 2 O(g) ΔH ∘ rxn =−802.3kJ

13 - Determine the mass of CO 2 produced by burning enough carbon (in the form of charcoal) to produce 530kJ of heat.

C(s)+O 2 (g)→CO 2 (g)ΔH ∘ rxn =−393.5kJ

14 - In the following experiment, a coffee-cup calorimeter containing 100 mL of H 2 O is used. The initial temperature of the calorimeter is 23.0 ∘ C If 5.70g of CaCl 2 is added to the calorimeter, what will be the final temperature of the solution in the calorimeter? The heat of solution ΔH soln of CaCl 2 is −82.8 kJ/mol.

#### Solution Preview

1-The air in an inflated balloon (defined as the system) is warmed over a toaster and absorbs 130J of heat. As it expands, it does 76kJ of work. What is the change in internal energy for the system?

Answer:

ΔE=q+w

Anything absorbed is + and any SYSTEM doing work is - .

130J + - 76000J= -7.587 x 10 ^ 4.

2-A piston has an external pressure of 8.00 atm How much work has been done in joules if the cylinder goes from a volume of 0.140 liters to 0.450 liters.

Answer:

(0.450 - 0.140) x 8.0=2.48 J

3-A volume of 105mL of H 2 O is initially at room temperature (22.0 ∘ C ). A chilled steel rod at 2.00 ∘ C is placed in the water. If the final temperature of the system is 21.3 ∘ C , what is the mass of the steel bar?

Use the following values:

specific heat of water = 4.18 J/(g⋅ ∘ C)

specific heat of steel = 0.452 J/(g⋅ ∘ C)

Answer:

105 x 4.18 x 22 + MS x .452 x 2 = 105 x 4.18 x 21.3 + MS x .452 x 21.3

MS = mass of steel

Solve for MS.

energy gained by the steel = the energy given up by the water

MS x .452 x [21.3 -2] = 105 x 4.18 x [22 - 21.3]

mass of steel = 35.22 g

4-The specific heat of water is 4.18 J/(g⋅ ∘ C) . Calculate the molar heat capacity of water.

Answer:

specific heat of water is 4.18 J/g-K

mole of water = 1802 g

molar heat capacity = (4.18 ...

#### Solution Summary

The various thermodynamics questions are solved. The specific heat of solvers are given.