Q: What is the formula mass of $$\mathrm{CO}_2$$? (Atomic masses: C = 12.0, O = 16.0)

$$12.0 + 2 \times 16.0 = 44.0$$

Question 1

Which statement best describes the most important characteristic of a chemical compound?

Accepted Answer

A compound is composed of atoms in fixed, definite proportions in all samples.

Question 2

Which of the following is NOT an example of a compound found in everyday life?

Accepted Answer

Oxygen gas

Question 3

What does a chemical formula primarily indicate about a compound?

Accepted Answer

The elements present and the relative number of atoms of each element.

Question 4

Which of the following best explains why understanding chemical formulas is important for understanding the properties of compounds?

Accepted Answer

Chemical formulas represent the molecular structure, which determines the macroscopic properties.

Question 5

A compound contains 2 atoms of hydrogen and 1 atom of oxygen. What is its chemical formula?

Accepted Answer

$$\mathrm{H}_2\mathrm{O}$$

Question 6

Which type of compound is formed when a metal reacts with a nonmetal?

Accepted Answer

Ionic compound

Question 7

What is the formula mass of $$\mathrm{CO}_2$$? (Atomic masses: C = 12.0, O = 16.0)

Accepted Answer

$$12.0 + 2 	imes 16.0 = 44.0$$

Question 8

Why is formula mass important in chemical calculations?

Accepted Answer

It is used to calculate the quantities of compounds in chemical reactions.

Question 9

Which of the following compounds is molecular?

Accepted Answer

$$\mathrm{CO}_2$$

Question 10

A student wants to name a compound with the formula $$\mathrm{Na}_2\mathrm{SO}_4. $$What type of compound is this and what naming system should be used?

Accepted Answer

Ionic compound; use the names of the ions.

Question 11

If a compound contains cations and anions, what is the most likely type of compound?

Accepted Answer

Ionic compound

Question 12

Which of the following statements about formula mass is TRUE?

Accepted Answer

Formula mass is the sum of the atomic masses of all atoms in the chemical formula.

Question 13

Which of the following best describes the difference between molecular and ionic compounds?

Accepted Answer

Molecular compounds are composed of nonmetals, while ionic compounds are composed of metals and nonmetals.

Question 14

A compound has the formula $$\mathrm{C}_6\mathrm{H}_{12}\mathrm{O}_6. $$What is the total number of atoms in one molecule of this compound?

Accepted Answer

$$6 + 12 + 6 = 24$$

Question 15

Which of the following is a correct statement about the naming of compounds?

Accepted Answer

There are systematic rules for naming different types of compounds.

Question 16

If you know the elements in a compound, what else do you need to write its chemical formula?

Accepted Answer

The relative number of atoms of each element.

Question 17

Which of the following is a real-world application of understanding formula mass?

Accepted Answer

Calculating the amount of reactants needed for a chemical reaction.

Question 18

A compound is found to contain only sodium and chlorine. What is the most likely chemical formula for this compound?

Accepted Answer

$$\mathrm{NaCl}$$

Question 19

Which statement best explains why the properties of compounds differ from those of their constituent elements?

Accepted Answer

The combination of atoms in fixed proportions creates new substances with unique properties.

Question 20

A chemist needs to determine the formula mass of $$\mathrm{H}_2\mathrm{SO}_4. $$Given atomic masses: H = 1.0, S = 32.0, O = 16.0. What is the formula mass?

Accepted Answer

$$2 	imes 1.0 + 32.0 + 4 	imes 16.0 = 98.0$$

Compounds, Chemical Formulas, and Formula Mass in Chemistry

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