Question 1

Which of the following statements best explains why the Kelvin scale is preferred in scientific temperature measurements over the Celsius and Fahrenheit scales?

Accepted Answer

The Kelvin scale starts at absolute zero, which is the lowest possible temperature, making it directly proportional to the average kinetic energy of particles.

Question 2

A student measures the mass of a metal cylinder as 45.67 g and its volume as 12.3 mL. What is the density of the cylinder, and how many significant figures should the answer have?

Accepted Answer

Density = $$3.71\ \mathrm{g/mL}$$; answer should have 3 significant figures.

Question 3

Which of the following best describes the difference between a compound and a mixture?

Accepted Answer

A compound consists of two or more elements chemically bonded in fixed proportions, while a mixture contains two or more substances physically combined in variable proportions.

Question 4

A sample contains $$3.01 	imes 10$$^{23}$$ molecules of water. How many moles of water does this sample contain?

Accepted Answer

$$0.500$$ moles

Question 5

Which of the following is an example of a heterogeneous mixture?

Accepted Answer

Salad dressing with oil and vinegar

Question 6

Which of the following best explains why the ionization energy generally increases across a period (row) in the periodic table?

Accepted Answer

As you move across a period, the effective nuclear charge increases, pulling electrons closer and making them harder to remove.

Question 7

A student needs to convert $$250$$ milliliters ($$\mathrm{mL}) to $$liters ($$\mathrm{L}). $$Which conversion factor should they use, and what is the correct answer?

Accepted Answer

Use $$1\ \mathrm{L} = 1000\ \mathrm{mL}$$; $$250\ \mathrm{mL} = 0.250\ \mathrm{L}$$

Question 8

Which of the following statements about isotopes is correct?

Accepted Answer

Isotopes of an element have the same number of protons but different numbers of neutrons.

Question 9

Which of the following best describes the Law of Conservation of Mass?

Accepted Answer

In a chemical reaction, mass is neither created nor destroyed.

Question 10

A neutral atom of sodium ($$^{23}_{11}\mathrm{Na}) $$has how many protons, neutrons, and electrons?

Accepted Answer

11 protons, 12 neutrons, 11 electrons

Question 11

Which of the following equations correctly represents Coulomb’s law for the force between two charged particles?

Accepted Answer

$$F = k \frac{q_1$ q_2$}{r^2$}$$

Question 12

Which of the following best explains why atomic size increases down a group in the periodic table?

Accepted Answer

As you move down a group, additional electron shells are added, increasing the distance between the nucleus and the outermost electrons.

Question 13

A sample of copper has two naturally occurring isotopes: $$^{63}\mathrm{Cu} (69.2$$% abundance, mass = 62.93 u) and $$^{65}\mathrm{Cu} (30.8$$% abundance, mass = 64.93 u). What is the average atomic mass of copper?

Accepted Answer

$$63.55\ \mathrm{u}$$

Question 14

Which of the following is an example of a physical property that is intrinsic to a substance?

Accepted Answer

Density

Question 15

Which of the following best describes why ionization energy decreases down a group in the periodic table?

Accepted Answer

Electrons are farther from the nucleus and experience more shielding, making them easier to remove.

Question 16

A chemist has $$18.0$$ grams of water ($$\mathrm{H}_2\mathrm{O}). $$How many moles of water does this represent? (Molar mass of $$\mathrm{H}_2\mathrm{O} = 18.0\ \mathrm{g/mol})$$

Accepted Answer

$$1.00$$ mole

Question 17

Which of the following is the best example of a scientific law?

Accepted Answer

The total mass of substances does not change during a chemical reaction.

Question 18

Which of the following best describes the concept of effective nuclear charge ($$Z_{\mathrm{eff}}$$)?

Accepted Answer

It is the net positive charge experienced by an electron in a multi-electron atom, accounting for both the actual nuclear charge and the shielding effect of other electrons.

Question 19

A student wants to convert $$5.00$$ kilometers to meters. Which equation should they use, and what is the correct answer?

Accepted Answer

$$5.00\ \mathrm{km} 	imes \frac{1000\ \mathrm{m}}{1\ \mathrm{km}} = 5000\ \mathrm{m}$$

General Chemistry Study Guide: Units, Measurement, Atoms, and Atomic Structure

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