Q: A sample of ethanol has a mass of 46.0 g and a volume of 58.0 mL. What is its density?

$$\text{Density} = \frac{46.0\ \text{g}}{58.0\ \text{mL}} = 0.793\ \text{g/mL}$$

Q: A neutral atom of magnesium has an atomic number of 12 and a mass number of 24. How many neutrons does it contain?

$$\text{Neutrons} = 24 - 12 = 12$$

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

$$q = (4.18\ \text{J/g}^\circ\text{C})(50.0\ \text{g})(75.0 - 25.0)\ ^\circ\text{C} = 10,450\ \text{J}$$

Question 1

Which of the following best describes a homogeneous mixture?

Accepted Answer

A mixture in which the composition is uniform throughout, such as salt dissolved in water.

Question 2

A student measures the mass of a metal sample as 12.34 g, 12.35 g, and 12.33 g in three trials. The true mass is 12.80 g. Which statement best describes the measurements?

Accepted Answer

The measurements are precise but not accurate.

Question 3

Which of the following statements about significant figures is correct?

Accepted Answer

Conversion factors are considered to have an infinite number of significant figures.

Question 4

A sample of ethanol has a mass of 46.0 g and a volume of 58.0 mL. What is its density?

Accepted Answer

$$	ext{Density} = \frac{46.0\ 	ext{g}}{58.0\ 	ext{mL}} = 0.793\ 	ext{g/mL}$$

Question 5

Which of the following best illustrates the Law of Constant Composition?

Accepted Answer

Water from any source always contains hydrogen and oxygen in a 2:1 ratio by atoms.

Question 6

A neutral atom of magnesium has an atomic number of 12 and a mass number of 24. How many neutrons does it contain?

Accepted Answer

$$	ext{Neutrons} = 24 - 12 = 12$$

Question 7

Which group in the periodic table contains elements that are all highly reactive metals?

Accepted Answer

Group IA (Alkali metals)

Question 8

Which of the following best explains why sodium forms a $$+1$$ ion and chlorine forms a $$-1$$ ion in sodium chloride?

Accepted Answer

Sodium loses one electron to achieve an octet, while chlorine gains one electron to achieve an octet.

Question 9

Which of the following is the correct electron configuration shorthand for a neutral atom of sulfur ($$Z=16$$)?

Accepted Answer

$$[	ext{Ne}]\ 3s^2$\ 3p^4$

Question 10

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

Accepted Answer

$$q = (4.18\ 	ext{J/g}^\circ	ext{C})(50.0\ 	ext{g})(75.0 - 25.0)\ ^\circ	ext{C} = 10,450\ 	ext{J}$$

Question 11

Which of the following best describes the Bohr model of the atom?

Accepted Answer

Electrons orbit the nucleus in fixed energy levels without radiating energy.

Question 12

Which of the following is a chemical change?

Accepted Answer

Iron rusting in moist air.

Question 13

A cation of aluminum has 13 protons, 14 neutrons, and 10 electrons. What is its charge?

Accepted Answer

$$+3$$

Question 14

Which of the following statements about quantum physics is correct?

Accepted Answer

Energy is quantized and electrons can only occupy specific energy levels.

Question 15

Which of the following is the correct formula for the compound formed between magnesium and chlorine?

Accepted Answer

$$	ext{MgCl}_2$$

Question 16

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

Accepted Answer

Matter is neither created nor destroyed in a chemical reaction.

Question 17

Which of the following elements is most likely to form an anion?

Accepted Answer

Chlorine

Question 18

A sample contains $$3.0 	imes 10$$^{24}$$ atoms of carbon. How many moles of carbon are present? (N_A = 6.022$$ 	imes $$10^{23}$$\ 	ext{mol}^{-1}$$)

Accepted Answer

$$\frac{3.0 	imes 10$$^{24}$$}{6.022 	imes 10$$^{23}$$} = 4.98\ 	ext{mol}$$

Question 19

Which of the following best explains why noble gases are generally unreactive?

Accepted Answer

They have a complete octet in their valence shell.

CHE 111: General Chemistry I – Study Guide (Chapters 1–4)

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