Q: A reaction releases 250 kJ of heat and does 50 kJ of work on the surroundings. What is the change in internal energy ($\Delta E$) of the system?

$\displaystyle -300\ \text{kJ}$

Q: Which of the following is the correct value for Avogadro’s number?

$\displaystyle 6.022 \times 10^{23}$

Question 1

Which of the following best describes a heterogeneous mixture?

Accepted Answer

A mixture in which the composition is not uniform and different parts can be visually distinguished, such as sand in water.

Question 2

Which law is demonstrated when 12 g of carbon reacts with 32 g of oxygen to form 44 g of carbon dioxide?

Accepted Answer

Law of Conservation of Mass

Question 3

Which statement about Dalton’s atomic theory is correct?

Accepted Answer

Atoms of different elements combine in simple whole-number ratios to form compounds.

Question 4

A sample contains 3.01 × 10^{23} molecules of CO_2. What is the mass of this sample? (Molar mass of CO_2 = 44.0 g/mol)

Accepted Answer

$\displaystyle 22.0\ 	ext{g}$

Question 5

Which of the following is an example of an endothermic process?

Accepted Answer

Melting of ice in a drink

Question 6

Which equation correctly relates the energy change ($\Delta E$) of a system to heat ($q$) and work ($w$)?

Accepted Answer

$\displaystyle \Delta E = q + w$

Question 7

A gas occupies 2.00 L at 1.00 atm and 300 K. If the pressure is doubled and the temperature is increased to 600 K, what is the new volume?

Accepted Answer

$\displaystyle 1.00\ 	ext{L}$

Question 8

Which of the following best explains why helium balloons rise in air?

Accepted Answer

Helium is less dense than air, so the buoyant force pushes the balloon upward.

Question 9

Which of the following statements about the kinetic molecular theory of gases is FALSE?

Accepted Answer

Gas particles exert attractive forces on each other.

Question 10

A 1.00 mol sample of an ideal gas at 273 K and 1.00 atm occupies what volume? (Use $R = 0.0821\ 	ext{L} \cdot 	ext{atm} / 	ext{mol} \cdot 	ext{K}$)

Accepted Answer

$\displaystyle 22.4\ 	ext{L}$

Question 11

Which of the following best describes the law of multiple proportions?

Accepted Answer

If two elements form more than one compound, the masses of one element that combine with a fixed mass of the other are in ratios of small whole numbers.

Question 12

Which of the following is the correct expression for the root mean square speed ($u_{rms}$) of a gas molecule?

Accepted Answer

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

Question 13

A reaction releases 250 kJ of heat and does 50 kJ of work on the surroundings. What is the change in internal energy ($\Delta E$) of the system?

Accepted Answer

$\displaystyle -300\ 	ext{kJ}$

Question 14

Which of the following statements about real gases is correct?

Accepted Answer

Real gases deviate from ideal behavior due to intermolecular forces and finite molecular volume.

Question 15

Which of the following is the correct value for Avogadro’s number?

Accepted Answer

$\displaystyle 6.022 	imes 10^{23}$

Question 16

Which of the following best describes the process of diffusion?

Accepted Answer

The mixing of gas molecules by random motion.

Question 17

A sample of nitrogen gas is collected over water at 25°C. The total pressure is 755 mmHg, and the vapor pressure of water at 25°C is 23.8 mmHg. What is the partial pressure of nitrogen?

Accepted Answer

$\displaystyle 731.2\ 	ext{mmHg}$

Question 18

Which of the following is a correct statement about enthalpy ($\Delta H$)?

Accepted Answer

Enthalpy is the heat absorbed or released at constant pressure.

Question 19

Which of the following best explains why the temperature of a gas increases when it is compressed rapidly?

Accepted Answer

Work is done on the gas, increasing its internal energy.

Question 20

Which of the following is the correct relationship for the pressure-volume work done by a gas during expansion at constant pressure?

Accepted Answer

$\displaystyle w = -P \Delta V$

CHEM162 Midterm Exam Study Guide: Key Concepts in General Chemistry

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