Question 1

Which of the following best describes the difference between an empirical formula and a molecular formula?

Accepted Answer

An empirical formula gives the smallest whole-number ratio of atoms in a compound, while a molecular formula gives the actual number of atoms of each element in a molecule.

Question 2

Which of the following compounds is represented by the empirical formula $$\mathrm{CH_2$}$$?

Accepted Answer

$$\mathrm{C_2H_4}$$

Question 3

A sample of magnesium chloride ($$\mathrm{$$MgCl_2$$}) $$has a mass of 190 g. What is the number of moles of $$\mathrm{$$MgCl_2$$} in $$the sample? (Molar mass of $$\mathrm{$$MgCl_2$$} = 95 g/$$mol)

Accepted Answer

2 mol

Question 4

Which of the following statements about ionic compounds is correct?

Accepted Answer

The sum of the charges of the cations and anions in the formula must be zero.

Question 5

What is the formula of the ionic compound formed between $$\mathrm{Al$$^{3+}$$}$$ and $$\mathrm{O$$^{2-}$$}$$?

Accepted Answer

$$\mathrm{Al_2O_3}$$

Question 6

Which of the following is a correct statement about the molar mass of a compound?

Accepted Answer

The molar mass is numerically equivalent to the formula mass, but expressed in g/mol.

Question 7

A compound contains 5.88 g of hydrogen and 94.12 g of oxygen. What is the empirical formula of the compound?

Accepted Answer

$$\mathrm{HO}$$

Question 8

Which of the following best describes a covalent bond?

Accepted Answer

A bond formed by the sharing of electrons between two nonmetal atoms.

Question 9

What is the mass percent of chlorine in $$\mathrm{$$MgCl_2$$}$$? (Mg = 24 g/mol, Cl = 35.5 g/mol)

Accepted Answer

75%

Question 10

Which of the following elements exists naturally as a diatomic molecule?

Accepted Answer

Oxygen

Question 11

Given the empirical formula $$\mathrm{CH_2$}$$ and a molar mass of 56 g/mol, what is the molecular formula of the compound? (Empirical formula mass = 14 g/mol)

Accepted Answer

$$\mathrm{C_4H_8}$$

Question 12

Which of the following is a correct representation of the structural formula for hydrogen peroxide?

Accepted Answer

$$\mathrm{H-O-O-H}$$

Question 13

Which of the following is NOT a correct step in determining the empirical formula from mass percent data?

Accepted Answer

Divide all mole values by the largest number of moles.

Question 14

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

Accepted Answer

A chemical compound always contains the same proportion of elements by mass.

Question 15

Which of the following is the correct balanced equation for the combustion of methane ($$\mathrm{CH_4$}) in $$oxygen?

Accepted Answer

$$\mathrm{CH_4$ + 2O_2 \rightarrow CO_2$ + 2H_2O}$$

Question 16

Which of the following is a property of water that is different from its constituent elements?

Accepted Answer

Water is a liquid at room temperature, while hydrogen and oxygen are gases.

Question 17

Which of the following is the correct formula for calcium perchlorate?

Accepted Answer

$$\mathrm{Ca($$ClO_4$$)_2}$$

Question 18

Which of the following best describes a metallic bond?

Accepted Answer

A bond formed by the pooling of valence electrons among metal atoms.

Question 19

If a compound has an empirical formula of $$\mathrm{HO}$$ and a molar mass of 34 g/mol, what is its molecular formula?

Accepted Answer

$$\mathrm{H_2O_2}$$

Question 20

Which of the following is a correct statement about the composition of a compound?

Accepted Answer

The mass percent of each element in a compound remains the same regardless of the sample size.

Chapter 3: Molecules, Compounds, and Chemical Equations – Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards