Question 1

A 50.0 g piece of copper (specific heat $$C_s = 0.387 \ \mathrm{J/g\cdot ^\circ C}) at$$ $$100.0\ ^\circ \mathrm{C} is $$dropped into 100.0 g of water at $$25.0\ ^\circ \mathrm{C}. $$What is the final temperature at thermal equilibrium? (Assume no heat loss to the surroundings, $$C_s$$ for water $$= 4.18 \ \mathrm{J/g\cdot ^\circ C})$$

Accepted Answer

$$T_f = 28.6\ ^\circ \mathrm{C}$$

Question 2

Which of the following statements best describes the law of conservation of energy as it applies to a chemical reaction in a coffee cup calorimeter?

Accepted Answer

Energy is neither created nor destroyed; it is transferred between the system and the surroundings.

Question 3

A reaction has $$\Delta H = -350\ \mathrm{kJ}. $$Which of the following is true about this reaction?

Accepted Answer

It is exothermic and releases heat to the surroundings.

Question 4

How much energy (in Joules) is required to raise the temperature of 200.0 g of water from $$20.0\ ^\circ \mathrm{C} to$$ $$50.0\ ^\circ \mathrm{C}$$? ($$C_s$$ for water $$= 4.18 \ \mathrm{J/g\cdot ^\circ C})$$

Accepted Answer

$$q = 25,080\ \mathrm{J}$$

Question 5

Which of the following best explains why metals like copper are used for cookware, based on their specific heat capacities?

Accepted Answer

Copper has a low specific heat, so it heats up quickly and transfers heat efficiently.

Question 6

A chemical reaction in a coffee cup calorimeter causes the temperature of the water to increase. Which of the following is true?

Accepted Answer

The reaction is exothermic and $$q_{rxn} is $$negative.

Question 7

If 100.0 g of silver ($$C_s = 0.234 \ \mathrm{J/g\cdot ^\circ C}) at$$ $$80.0\ ^\circ \mathrm{C} is $$placed in 200.0 g of water at $$20.0\ ^\circ \mathrm{C}$$, what is the final temperature at equilibrium? ($$C_s$$ for water $$= 4.18 \ \mathrm{J/g\cdot ^\circ C})$$

Accepted Answer

$$T_f = 21.3\ ^\circ \mathrm{C}$$

Question 8

Which of the following is the correct relationship for calculating the energy change of a system?

Accepted Answer

$$\Delta E = E_{final} - E_{initial}$$

Question 9

A 10.0 g sample of gold ($$C_s = 0.129 \ \mathrm{J/g\cdot ^\circ C}) $$absorbs 25.8 J of heat. If the initial temperature was $$25.0\ ^\circ \mathrm{C}$$, what is the final temperature?

Accepted Answer

$$T_f = 45.0\ ^\circ \mathrm{C}$$

Question 10

Which of the following real-life scenarios best illustrates the concept of thermal equilibrium?

Accepted Answer

A hot metal spoon placed in a cup of cold water eventually reaches the same temperature as the water.

Question 11

Which of the following statements about the system and surroundings in a calorimetry experiment is correct?

Accepted Answer

The system is the chemical reaction or process being studied, and the surroundings are the water and calorimeter.

Question 12

Which of the following best describes why water is effective at moderating temperature changes in the environment?

Accepted Answer

Water has a high specific heat capacity, so it resists temperature changes.

Question 13

A student dissolves 5.00 g of NaOH(s) in water in a coffee cup calorimeter. The temperature of the water increases. Which of the following is true about the process?

Accepted Answer

The dissolution of NaOH is exothermic.

Question 14

Which of the following conversions is correct for energy units?

Accepted Answer

$$1\ \mathrm{cal} = 4.184\ \mathrm{J}$$

Question 15

A 250.0 g sample of sand ($$C_s = 0.830 \ \mathrm{J/g\cdot ^\circ C}) is $$heated from $$20.0\ ^\circ \mathrm{C} to$$ $$100.0\ ^\circ \mathrm{C}. $$How much heat is absorbed?

Accepted Answer

$$q = 16,600\ \mathrm{J}$$

Question 16

Which of the following best describes the difference between kilojoules and kilocalories as used in science and nutrition?

Accepted Answer

Kilojoules are used by scientists, while kilocalories are used by nutritionists and the general public.

Thermochemistry and Quantum-Mechanical Model of the Atom: Study Notes

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