Q: A gas mixture contains 2.0 mol of $$\mathrm{O}_2$$ and 3.0 mol of $$\mathrm{N}_2 at a $$total pressure of 5.0 atm. What is the partial pressure of $$\mathrm{O}_2$$?

$$P_{O_2$} = \frac{2.0}{2.0+3.0} \times 5.0 = 2.0\ \mathrm{atm}$$

Question 1

Which of the following statements correctly describes what happens to an element that is oxidized in a redox reaction?

Accepted Answer

It loses electrons and its oxidation number becomes more positive.

Question 2

A sample of gas occupies 2.50 L at 1.00 atm and 300 K. What will be its volume at 2.00 atm and 400 K? (Assume the amount of gas is constant.)

Accepted Answer

$$V_2$$ = \frac{$$P_1$$ $$V_1$$ $$T_2$$}{$$T_1$$ $$P_2$$} = \frac{(1.00)(2.50)(400)}{(300)(2.00)} = 1.67\ \mathrm{L}$$

Question 3

Which of the following is an example of a closed system?

Accepted Answer

A sealed soda can where heat can be exchanged but matter cannot.

Question 4

A 50.0 g sample of water is heated from 25.0 $$^\circC to 75.0$$ $$^\circC. $$What is the amount of heat absorbed? (Specific heat of water $$c = 4.18\ \mathrm{J/gK})$$

Accepted Answer

$$q = mc\Delta T = (50.0)(4.18)(75.0-25.0) = 10,450\ \mathrm{J}$$

Question 5

Which of the following best describes the relationship between wavelength ($$\lambda) $$and frequency ($$v) of $$light?

Accepted Answer

They are inversely proportional: as wavelength increases, frequency decreases.

Question 6

A gas mixture contains 2.0 mol of $$\mathrm{O}_2$$ and 3.0 mol of $$\mathrm{N}_2 at a $$total pressure of 5.0 atm. What is the partial pressure of $$\mathrm{O}_2$$?

Accepted Answer

$$P_{O_2$} = \frac{2.0}{2.0+3.0} 	imes 5.0 = 2.0\ \mathrm{atm}$$

Question 7

Which of the following statements about the first law of thermodynamics is correct?

Accepted Answer

The total energy of an isolated system is constant.

Question 8

Which of the following is true about the energy change when chemical bonds are formed?

Accepted Answer

Energy is released when bonds are formed.

Question 9

A bomb calorimeter contains 1.00 g of a substance that, when combusted, raises the temperature of the calorimeter by 2.50 K. If the heat capacity of the calorimeter is $$5.00\ \mathrm{kJ/K}$$, what is the heat released by the reaction?

Accepted Answer

$$Q_{rxn} = -Q_{cal} = -(5.00\ \mathrm{kJ/K})(2.50\ \mathrm{K}) = -12.5\ \mathrm{kJ}$$

Question 10

Which of the following electron configurations represents a sodium ion ($$\mathrm{Na}^+$$)?

Accepted Answer

$$1s^2$$\ $$2s^2$$\ $$2p^6$$

Question 11

Which quantum number determines the shape of an orbital?

Accepted Answer

The azimuthal quantum number $$l$$

Question 12

A photon has a wavelength of $$4.00 	imes 10$$^{-7}$$\ \mathrm{m}. $$What is its frequency? ($$c = 3.00 	imes 10^8$\ \mathrm{m/s})$$

Accepted Answer

$$v = \frac{c}{\lambda} = \frac{3.00 	imes 10^8$}{4.00 	imes 10$$^{-7}$$} = 7.50 	imes 10$$^{14}$$\ \mathrm{Hz}$$

Question 13

Which of the following best describes Hund’s rule?

Accepted Answer

Electrons fill degenerate orbitals singly before pairing up.

Question 14

Which of the following is a state function?

Accepted Answer

Enthalpy ($$H)$$

Question 15

A 10.0 g piece of metal at 100.0 $$^\circC is $$placed in 50.0 g of water at 25.0 $$^\circC. $$The final temperature is 28.0 $$^\circC. $$What is the specific heat of the metal? ($$c_{water} = 4.18\ \mathrm{J/gK})$$

Accepted Answer

$$q_{metal} = -q_{water}$$, $$m_{metal} c_{metal} \Delta T_{metal} = -m_{water} c_{water} \Delta T_{water}$$, $$c_{metal} = \frac{-m_{water} c_{water} \Delta T_{water}}{m_{metal} \Delta T_{metal}} = \frac{-(50.0)(4.18)(28.0-25.0)}{10.0(28.0-100.0)} = 0.86\ \mathrm{J/gK}$$

Question 16

Which of the following statements about the kinetic molecular theory of gases is NOT correct?

Accepted Answer

Gas particles experience strong attractive forces.

Question 17

Which of the following is the correct electron configuration for an excited state of carbon ($$Z=6$$)?

Accepted Answer

$$1s^2$$\ $$2s^1$$\ $$2p^3$$

Question 18

Which of the following best describes the Pauli exclusion principle?

Accepted Answer

No two electrons in an atom can have the same set of four quantum numbers.

Question 19

A chemical reaction in a coffee cup calorimeter absorbs 250 J of heat from the solution. Which of the following statements is true?

Accepted Answer

The reaction is endothermic and $$q_{rxn} = +250\ \mathrm{J}.$$

Introduction to Chemistry: Study Notes on Redox, Gases, Thermochemistry, and Atomic Structure

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