Q: A gas absorbs 5.973 kJ of heat and does 0.589 kJ of work by pushing a piston. What is the change in internal energy ($$\Delta E) of $$the gas?

$$ \Delta E = 5.384 \text{ kJ} $$

Q: Which formula is used to calculate the heat absorbed or released by a substance?

$$ q = m \times C_s \times \Delta T $$

Q: A 5.009 g lump of gold at 37.0$$^\circC $$absorbs 11.04 J of heat energy. What is its final temperature? ($$C_{\text{gold}} = 0.129 \text{ J/g}^\circ\text{C})$$

$$ T_f = 54.1^\circ \text{C} $$

Q: What is the relationship between the energy lost by the system and the energy gained by the surroundings?

$$ \Delta E_{\text{sys}} = -\Delta E_{\text{surr}} $$

Question 1

Which of the following best defines the 'system' in thermodynamics?

Accepted Answer

The part of the universe that is undergoing a change or reaction.

Question 2

If a chemical reaction in a beaker absorbs heat from the surroundings, which of the following statements is correct?

Accepted Answer

The reaction is endothermic and $$q$$ for the system is positive.

Question 3

Which equation correctly expresses the First Law of Thermodynamics for a closed system?

Accepted Answer

$$ \Delta E = q + w $$

Question 4

A gas absorbs 5.973 kJ of heat and does 0.589 kJ of work by pushing a piston. What is the change in internal energy ($$\Delta E) of $$the gas?

Accepted Answer

$$ \Delta E = 5.384 	ext{ kJ} $$

Question 5

Which of the following scenarios describes a negative value for work ($$w) $$done by the system?

Accepted Answer

The system expands against an external pressure.

Question 6

Calculate the work done (in Joules) when a balloon expands from 2.0 L to 3.8 L on the moon, where the atmospheric pressure is 0.00500 atm. ($$1.00 	ext{ atm} \cdot 	ext{L} = 101.31 	ext{ J})$$

Accepted Answer

$$ w = -0.90 	ext{ J} $$

Question 7

Which formula is used to calculate the heat absorbed or released by a substance?

Accepted Answer

$$ q = m 	imes C_s 	imes \Delta T $$

Question 8

A 5.009 g lump of gold at 37.0$$^\circC $$absorbs 11.04 J of heat energy. What is its final temperature? ($$C_{	ext{gold}} = 0.129 	ext{ J/g}^\circ	ext{C})$$

Accepted Answer

$$ T_f = 54.1^\circ 	ext{C} $$

Question 9

In a bomb calorimeter, why does all the energy from the reaction get converted to heat energy?

Accepted Answer

Because $$\Delta V = 0$$, so no work is done by the system.

Question 10

Which of the following best describes an exothermic reaction in a calorimeter?

Accepted Answer

The temperature of the calorimeter increases as heat is released by the system.

Question 11

What is the relationship between the energy lost by the system and the energy gained by the surroundings?

Accepted Answer

$$ \Delta E_{	ext{sys}} = -\Delta E_{	ext{surr}} $$

Question 12

A 100.1 L balloon loses 206 J of heat, and the overall change in internal energy is $$-458.7 J. $$What is the value of work ($$w) $$for the system?

Accepted Answer

$$ w = -252.7 	ext{ J} $$

Question 13

Which equation defines enthalpy ($$H) $$for a system?

Accepted Answer

$$ H = E + PV $$

Question 14

A hot piece of iron (initially at 275.5$$^\circC) is $$placed in 200 g of water at 22.2$$^\circC. $$When thermal equilibrium is reached, the final temperature is 28.1$$^\circC. $$What is the mass of the piece of iron? ($$C_{	ext{iron}} = 0.449 	ext{ J/g}^\circ	ext{C}$$, $$C_{	ext{water}} = 4.184 	ext{ J/g}^\circ	ext{C})$$

Accepted Answer

21.6 g

Question 15

Which of the following is true for a constant pressure calorimeter (coffee cup calorimeter)?

Accepted Answer

The reaction is open to the atmosphere and pressure is constant.

Question 16

The reaction of one mole of sodium and water yields hydrogen gas and aqueous sodium chloride. If this reaction produces 367.5 kJ of heat and does 2.5 kJ of work, what are $$\Delta H$$ and $$\Delta E$$ for the reaction?

Accepted Answer

$$ \Delta H = 367.5 	ext{ kJ}, \Delta E = 365.0 	ext{ kJ} $$

Chapter 7: Thermochemistry and Thermodynamics – Study Notes

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