Question 1

A 2.00 L container holds a mixture of nitrogen and oxygen gases at 300 K and a total pressure of 1.00 atm. If the partial pressure of nitrogen is 0.70 atm, what is the mole fraction of oxygen in the mixture?

Accepted Answer

$$0.30$$

Question 2

Which of the following statements best explains why the rate of effusion of helium gas is higher than that of oxygen gas at the same temperature?

Accepted Answer

Helium has a lower molar mass, so according to Graham's Law, it effuses faster.

Question 3

A sample of gas occupies 5.00 L at 1.00 atm and 300 K. If the gas is compressed to 2.50 L and heated to 600 K, what is the new pressure, assuming ideal gas behavior?

Accepted Answer

$$P_2 = 4.00$$\ 	ext{atm}$$

Question 4

Which of the following best describes the kinetic molecular theory's explanation for the pressure exerted by a gas?

Accepted Answer

Gas pressure results from collisions of gas molecules with the walls of the container.

Question 5

A rigid container holds 2.00 mol of an ideal gas at 273 K. If the temperature is doubled and the volume remains constant, what happens to the average kinetic energy of the gas molecules?

Accepted Answer

It doubles.

Question 6

Which of the following equations correctly relates the root mean square velocity ($$u_{rms}) of a $$gas to its molar mass ($$M) $$and temperature ($$T$$)?

Accepted Answer

$$u_{rms} = \sqrt{\frac{3RT}{M}}$$

Question 7

A real gas deviates from ideal behavior at high pressures and low temperatures primarily because:

Accepted Answer

Intermolecular forces and the finite volume of gas particles become significant.

Question 8

Which of the following best describes the first law of thermodynamics?

Accepted Answer

The change in internal energy of a system equals the heat added to the system plus the work done on the system.

Question 9

A chemical reaction occurs in a coffee-cup calorimeter. The temperature of the solution increases. Which of the following statements is true?

Accepted Answer

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

Question 10

Which of the following equations correctly expresses the relationship between enthalpy change ($$\Delta H$$), internal energy change ($$\Delta E$$), pressure ($$P$$), and change in volume ($$\Delta V) at $$constant pressure?

Accepted Answer

$$\Delta H = \Delta E + P\Delta V$$

Question 11

A 50.0 g sample of water is heated from 25.0 $$^\circC to 75.0$$ $$^\circC. If $$the specific heat capacity of water is $$4.18\ 	ext{J/g} \cdot ^\circ	ext{C}$$, how much heat is absorbed?

Accepted Answer

$$q = 10,450\ 	ext{J}$$

Question 12

Which of the following best describes the photoelectric effect?

Accepted Answer

Electrons are ejected from a metal surface when it is exposed to light of sufficient frequency.

Question 13

According to the Bohr model, what happens when an electron in a hydrogen atom transitions from $$n=3 to$$ $$n=1$$?

Accepted Answer

A photon is emitted with energy equal to the difference between the two energy levels.

Question 14

Which of the following correctly expresses the energy of a photon in terms of Planck's constant ($$h) $$and frequency ($$
u$$)?

Accepted Answer

$$E = h
u$$

Question 15

Which of the following statements about atomic orbitals is correct?

Accepted Answer

The probability of finding an electron is highest near the nucleus for an s orbital.

Question 16

Which quantum number determines the shape of an atomic orbital?

Accepted Answer

Angular momentum quantum number ($$l)$$

Question 17

Which of the following best describes Heisenberg's uncertainty principle?

Accepted Answer

It is impossible to simultaneously know both the exact position and momentum of an electron.

Question 18

Which equation gives the de Broglie wavelength ($$\lambda) of a $$particle with mass $$m$$ and velocity $$v$$?

Accepted Answer

$$\lambda = \frac{h}{mv}$$

Question 19

A reaction has $$\Delta H = -250\ 	ext{kJ}$$ and $$\Delta E = -240\ 	ext{kJ}. If $$the reaction occurs at constant pressure and the system does 10 kJ of work on the surroundings, which of the following is true?

Accepted Answer

The values are consistent with $$\Delta H = \Delta E + P\Delta V.$$

Question 20

Which of the following best explains why the van der Waals equation is used for real gases?

Accepted Answer

It accounts for intermolecular attractions and the finite volume of gas molecules.

Exam 3 General Chemistry Study Guide: Gases, Thermochemistry, and Quantum-Mechanical Model of the Atom

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