Q: A laser emits light with a wavelength of $$500\ \mathrm{nm}. $$What is the frequency of this light? (Speed of light $$c = 3.00 \times 10^8$\ \mathrm{m/s})$$

$$6.00 \times 10$$^{14}$$\ \mathrm{Hz}$$

Q: Which of the following equations correctly relates the energy, wavelength, and frequency of electromagnetic radiation?

$$E = h \nu$$ and $$c = \lambda \nu$$

Question 1

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

Accepted Answer

The total energy of the universe is constant; energy can be transferred or transformed but not created or destroyed.

Question 2

A chemical reaction in a laboratory releases heat to its surroundings and causes the temperature of the solution to rise. Which of the following best describes this reaction?

Accepted Answer

It is an exothermic reaction because it releases heat.

Question 3

Given the reaction: $$2 \mathrm{H}_2(g) + \mathrm{O}_2(g) \rightarrow 2 \mathrm{H}_2\mathrm{O}(l)$$, and the standard enthalpy of formation for $$\mathrm{H}_2\mathrm{O}(l) is$$ $$-285.8\ \mathrm{kJ/mol}$$, what is the enthalpy change $$\Delta H$$ for the reaction as written?

Accepted Answer

$$-571.6\ \mathrm{kJ}$$

Question 4

A 50.0 g sample of metal at $$100.0\ ^\circ\mathrm{C} is $$placed in 100.0 g of water at $$25.0\ ^\circ\mathrm{C}. $$The final temperature of the system is $$30.0\ ^\circ\mathrm{C}. If $$the specific heat capacity of water is $$4.18\ \mathrm{J/g\cdot ^\circ C}$$, what is the specific heat capacity $$c of $$the metal? (Assume no heat loss to surroundings.)

Accepted Answer

$$0.42\ \mathrm{J/g\cdot ^\circ C}$$

Question 5

In a bomb calorimeter experiment, the combustion of 1.00 g of a substance increases the temperature of the calorimeter by $$2.50\ ^\circ\mathrm{C}. If $$the heat capacity of the calorimeter is $$10.0\ \mathrm{kJ/}^\circ\mathrm{C}$$, what is the heat released by the reaction?

Accepted Answer

$$25.0\ \mathrm{kJ}$$

Question 6

Which of the following correctly applies Hess's Law to determine the enthalpy change for a reaction?

Accepted Answer

The enthalpy change of a reaction is independent of the pathway and equals the sum of the enthalpy changes for each step.

Question 7

Which of the following is the correct definition of the standard enthalpy of formation ($$\Delta H_f^\circ$$)?

Accepted Answer

The enthalpy change when one mole of a compound is formed from its elements in their standard states at $$1\ \mathrm{atm}$$ and $$25\ ^\circ\mathrm{C}.$$

Question 8

Which region of the electromagnetic spectrum has the highest energy per photon?

Accepted Answer

Gamma rays

Question 9

The energy of a photon is given by $$E = h 
u. If $$the frequency $$
u of a $$photon is doubled, what happens to its energy?

Accepted Answer

The energy is doubled.

Question 10

A laser emits light with a wavelength of $$500\ \mathrm{nm}. $$What is the frequency of this light? (Speed of light $$c = 3.00 	imes 10^8$\ \mathrm{m/s})$$

Accepted Answer

$$6.00 	imes 10$$^{14}$$\ \mathrm{Hz}$$

Question 11

Which of the following best explains why metals often feel colder than wood at the same temperature?

Accepted Answer

Metals conduct heat away from your skin more efficiently due to higher thermal conductivity.

Question 12

A reaction has $$\Delta H = +150\ \mathrm{kJ}. $$Which of the following statements is true about this reaction?

Accepted Answer

The reaction is endothermic and absorbs heat.

Question 13

If the energy of a photon is $$3.31 	imes 10$$^{-19}$$\ \mathrm{J}$$, what is its wavelength? (Planck's constant $$h = 6.626 	imes 10$$^{-34}$$\ \mathrm{J\cdot s}$$, speed of light $$c = 3.00 	imes 10^8$\ \mathrm{m/s})$$

Accepted Answer

$$600\ \mathrm{nm}$$

Question 14

Which of the following equations correctly relates the energy, wavelength, and frequency of electromagnetic radiation?

Accepted Answer

$$E = h 
u$$ and $$c = \lambda 
u$$

Question 15

A student mixes 100.0 mL of $$1.00\ \mathrm{M}$$ HCl with 100.0 mL of $$1.00\ \mathrm{M}$$ NaOH in a coffee-cup calorimeter. The temperature of the solution rises from $$22.0\ ^\circ\mathrm{C} to$$ $$28.0\ ^\circ\mathrm{C}. $$Assuming the solution has a density of $$1.00\ \mathrm{g/mL}$$ and a specific heat capacity of $$4.18\ \mathrm{J/g\cdot ^\circ C}$$, what is the enthalpy change per mole of water formed?

Accepted Answer

$$-57.0\ \mathrm{kJ/mol}$$

Question 16

Which of the following best describes the relationship between wavelength and frequency in the electromagnetic spectrum?

Accepted Answer

As wavelength increases, frequency decreases.

Question 17

A reaction has the following enthalpy changes: $$A \rightarrow B$$, $$\Delta H_1$ = +50\ \mathrm{kJ}$$; $$B \rightarrow C$$, $$\Delta H_2$ = -30\ \mathrm{kJ}$$; $$C \rightarrow D$$, $$\Delta H_3$ = +20\ \mathrm{kJ}. $$What is the enthalpy change for $$A \rightarrow D$$?

Accepted Answer

$$+40\ \mathrm{kJ}$$

Question 18

Which of the following is a real-life application of Hess's Law?

Accepted Answer

Calculating the enthalpy change for the combustion of octane in car engines using known enthalpies of formation.

Question 19

Which of the following best explains why the standard enthalpy of formation for an element in its standard state is zero?

Accepted Answer

Because no energy is required to form an element from itself in its standard state.

Thermochemistry and Electronic Structure: Key Concepts and Calculations

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