Q: Which equation correctly calculates the formula mass of a compound?

$$\text{Formula mass} = \sum (\text{Number of atoms of each element} \times \text{Atomic mass of each element})$$

Question 1

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

Accepted Answer

An empirical formula shows the simplest whole-number ratio of elements, while a molecular formula shows the actual number of atoms of each element in a molecule.

Question 2

A compound contains 40.0% carbon, 6.7% hydrogen, and 53.3% oxygen by mass. What is the empirical formula of this compound?

Accepted Answer

$$\mathrm{CH}_2\mathrm{O}$$

Question 3

Given the empirical formula $$\mathrm{CH}_2$$ and a molar mass of $$70\ \mathrm{g/mol}$$, what is the molecular formula of the compound?

Accepted Answer

$$\mathrm{C}_5\mathrm{H}_{10}$$

Question 4

Which equation correctly calculates the formula mass of a compound?

Accepted Answer

$$	ext{Formula mass} = \sum (	ext{Number of atoms of each element} 	imes 	ext{Atomic mass of each element})$$

Question 5

A sample of an unknown hydrocarbon is burned in excess oxygen. The products are collected and found to be $$4.4\ \mathrm{g} of$$ $$\mathrm{CO}_2$$ and $$1.8\ \mathrm{g} of$$ $$\mathrm{H}_2\mathrm{O}. $$What is the empirical formula of the hydrocarbon?

Accepted Answer

$$\mathrm{CH}_4$$

Question 6

Which of the following is NOT evidence of a chemical reaction?

Accepted Answer

Bubbles form when water is boiled.

Question 7

What is the correct balanced equation for the combustion of methane ($$\mathrm{CH}_4) in $$oxygen?

Accepted Answer

$$\mathrm{CH}_4 + 2\ \mathrm{O}_2 \rightarrow \mathrm{CO}_2 + 2\ \mathrm{H}_2\mathrm{O}$$

Question 8

Which of the following is the correct name for $$\mathrm{HClO}_3$$?

Accepted Answer

Chloric acid

Question 9

A compound is found to contain 45.5% nickel and 54.5% chlorine by mass. What is its empirical formula?

Accepted Answer

$$\mathrm{NiCl}_2$$

Question 10

Which of the following best describes the process of combustion analysis?

Accepted Answer

A compound is burned in oxygen, and the masses of $$\mathrm{CO}_2$$ and $$\mathrm{H}_2\mathrm{O}$$ produced are measured to determine the original composition.

Question 11

What is the correct name for $$\mathrm{H}_2\mathrm{SO}_3$$?

Accepted Answer

Sulfurous acid

Question 12

Which of the following is the correct molecular formula for a straight-chain alkane with 7 carbon atoms?

Accepted Answer

$$\mathrm{C}_7\mathrm{H}_{16}$$

Question 13

Which of the following is the correct formula for the alkene with 4 carbon atoms?

Accepted Answer

$$\mathrm{C}_4\mathrm{H}_8$$

Question 14

Which of the following is the correct formula for the organic compound known as acetone?

Accepted Answer

$$\mathrm{CH}_3\mathrm{COCH}_3$$

Question 15

Which of the following is the correct balanced equation for the reaction of aluminum with sulfuric acid to form aluminum sulfate and hydrogen gas?

Accepted Answer

$$2\ \mathrm{Al}(s) + 3\ \mathrm{H}_2\mathrm{SO}_4(aq) \rightarrow \mathrm{Al}_2(\mathrm{SO}_4)_3(aq) + 3\ \mathrm{H}_2(g)$$

Question 16

Which of the following is the correct formula for the organic compound known as ethyne?

Accepted Answer

$$\mathrm{C}_2\mathrm{H}_2$$

Question 17

Which of the following is the correct formula for the organic compound known as methyl alcohol?

Accepted Answer

$$\mathrm{CH}_3\mathrm{OH}$$

Question 18

Which of the following best describes the function of a mass spectrometer in chemical analysis?

Accepted Answer

It separates ions based on their mass-to-charge ratio, allowing determination of molecular and atomic masses.

Chapter 3 Study Guide: Molecules, Compounds, and Chemical Equations

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