Q: A gas expands from 0.500 L to 2.00 L against a constant external pressure of 1.50 atm. Calculate the work done by the system in joules. $$1\ \text{L-atm} = 101.3\ \text{J}$$

$$w = -1.50\ \text{atm} \times (2.00\ \text{L} - 0.500\ \text{L}) = -2.25\ \text{L-atm} = -228\ \text{J}$$

Q: A 50.0 g sample of copper ($$c = 0.385\ \text{J/g}^\circ\text{C}) is $$heated from $$25.0^\circ\text{C} to$$ $$75.0^\circ\text{C}. $$How much heat is absorbed by the copper?

$$q = 0.385\ \text{J/g}^\circ\text{C} \times 50.0\ \text{g} \times (75.0 - 25.0)^\circ\text{C} = 962.5\ \text{J}$$

Q: A block of aluminum ($$c = 0.897\ \text{J/g}^\circ\text{C}) $$with a mass of 10.0 g cools from $$100.0^\circ\text{C} to$$ $$25.0^\circ\text{C}. $$What is the value and sign of $$q$$?

$$q = 0.897\ \text{J/g}^\circ\text{C} \times 10.0\ \text{g} \times (25.0 - 100.0)^\circ\text{C} = -673\ \text{J}$$

Q: A gas is compressed in a cylinder, and 500 J of work is done ON the gas while 200 J of heat is released by the gas to the surroundings. What is the change in internal energy ($$\Delta E) of $$the system?

$$\Delta E = -200\ \text{J} + 500\ \text{J} = +300\ \text{J}$$

Q: If 22.1 J of energy is required to heat a 14.2 g gold ring from $$16.7^\circ\text{C} to$$ $$28.8^\circ\text{C}$$, what is the specific heat ($$c) of $$gold?

$$c = \dfrac{22.1\ \text{J}}{14.2\ \text{g} \times (28.8 - 16.7)^\circ\text{C}} = 0.129\ \text{J/g}^\circ\text{C}$$

Q: Which of the following processes is exothermic?

A block of iron cooling from $$91.6^\circ\text{C} to$$ $$25.1^\circ\text{C}$$, releasing heat.

Question 1

Which of the following best describes the First Law of Thermodynamics?

Accepted Answer

The total amount of energy in the universe is assumed constant; energy can only be converted from one form to another.

Question 2

A gas expands from 0.500 L to 2.00 L against a constant external pressure of 1.50 atm. Calculate the work done by the system in joules. $$1\ 	ext{L-atm} = 101.3\ 	ext{J}$$

Accepted Answer

$$w = -1.50\ 	ext{atm} 	imes (2.00\ 	ext{L} - 0.500\ 	ext{L}) = -2.25\ 	ext{L-atm} = -228\ 	ext{J}$$

Question 3

Which of the following is NOT a state function?

Accepted Answer

Work

Question 4

A 50.0 g sample of copper ($$c = 0.385\ 	ext{J/g}^\circ	ext{C}) is $$heated from $$25.0^\circ	ext{C} to$$ $$75.0^\circ	ext{C}. $$How much heat is absorbed by the copper?

Accepted Answer

$$q = 0.385\ 	ext{J/g}^\circ	ext{C} 	imes 50.0\ 	ext{g} 	imes (75.0 - 25.0)^\circ	ext{C} = 962.5\ 	ext{J}$$

Question 5

Which scenario best illustrates the conversion of chemical energy to kinetic energy?

Accepted Answer

A battery powering a moving toy car.

Question 6

A block of aluminum ($$c = 0.897\ 	ext{J/g}^\circ	ext{C}) $$with a mass of 10.0 g cools from $$100.0^\circ	ext{C} to$$ $$25.0^\circ	ext{C}. $$What is the value and sign of $$q$$?

Accepted Answer

$$q = 0.897\ 	ext{J/g}^\circ	ext{C} 	imes 10.0\ 	ext{g} 	imes (25.0 - 100.0)^\circ	ext{C} = -673\ 	ext{J}$$

Question 7

Which of the following statements is TRUE regarding heat and work?

Accepted Answer

Neither heat nor work is a state function.

Question 8

A gas is compressed in a cylinder, and 500 J of work is done ON the gas while 200 J of heat is released by the gas to the surroundings. What is the change in internal energy ($$\Delta E) of $$the system?

Accepted Answer

$$\Delta E = -200\ 	ext{J} + 500\ 	ext{J} = +300\ 	ext{J}$$

Question 9

Which of the following best explains why a pan of water at $$50^\circ	ext{C}$$ contains more thermal energy than a cup of coffee at $$85^\circ	ext{C}$$?

Accepted Answer

The pan has a greater mass, so the total thermal energy is higher despite the lower temperature.

Question 10

If 22.1 J of energy is required to heat a 14.2 g gold ring from $$16.7^\circ	ext{C} to$$ $$28.8^\circ	ext{C}$$, what is the specific heat ($$c) of $$gold?

Accepted Answer

$$c = \dfrac{22.1\ 	ext{J}}{14.2\ 	ext{g} 	imes (28.8 - 16.7)^\circ	ext{C}} = 0.129\ 	ext{J/g}^\circ	ext{C}$$

Question 11

Which of the following processes is exothermic?

Accepted Answer

A block of iron cooling from $$91.6^\circ	ext{C} to$$ $$25.1^\circ	ext{C}$$, releasing heat.

Question 12

A 21.2 g block of iron ($$c = 0.449\ 	ext{J/g}^\circ	ext{C}) $$cools from $$91.6^\circ	ext{C} to$$ $$25.1^\circ	ext{C}. $$How much heat is released?

Accepted Answer

$$q = 0.449\ 	ext{J/g}^\circ	ext{C} 	imes 21.2\ 	ext{g} 	imes (25.1 - 91.6)^\circ	ext{C} = -633\ 	ext{J}$$

Question 13

Which of the following is the correct formula for calculating the amount of heat ($$q) $$absorbed or released by a substance?

Accepted Answer

$$q = c 	imes m 	imes (T_{final} - T_{initial})$$

Question 14

A balloon is inflated from 0.100 L to 1.85 L against an external pressure of 1.00 atm. How much work is done by the system in joules?

Accepted Answer

$$w = -1.00\ 	ext{atm} 	imes (1.85 - 0.100)\ 	ext{L} = -1.75\ 	ext{L-atm} = -177\ 	ext{J}$$

Question 15

Which of the following best describes potential energy?

Accepted Answer

Energy available by virtue of an object's position.

Question 16

A 1.2 g block of iron ($$c = 0.449\ 	ext{J/g}^\circ	ext{C}) $$absorbs 11.1 J of heat. If its initial temperature is $$20.0^\circ	ext{C}$$, what is its final temperature?

Accepted Answer

$$T_{final} = 20.0^\circ	ext{C} + \dfrac{11.1\ 	ext{J}}{0.449\ 	ext{J/g}^\circ	ext{C} 	imes 1.2\ 	ext{g}} = 40.6^\circ	ext{C}$$

Question 17

Which of the following is an example of radiant energy being converted to thermal energy?

Accepted Answer

Sunlight warming your skin.

chapter 5 lec 1

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