Question 1

Which of the following best illustrates the Law of Conservation of Mass in a real-world scenario?

Accepted Answer

When 10 g of hydrogen reacts completely with 80 g of oxygen to form water, the total mass of water produced is 90 g.

Question 2

A student decomposes 36.04 g of water into hydrogen and oxygen gases. According to the Law of Conservation of Mass, what is the combined mass of hydrogen and oxygen gases produced?

Accepted Answer

36.04 g

Question 3

A chemist analyzes two samples of water from different sources. Sample A contains 2.24 g of hydrogen and 17.76 g of oxygen. Sample B contains 1.12 g of hydrogen. According to the Law of Definite Proportions, how much oxygen should be present in Sample B?

Accepted Answer

8.00 g

Question 4

Which of the following best explains why the Law of Definite Proportions is also called the Law of Constant Composition?

Accepted Answer

Because a compound always contains the same elements in the same fixed ratio by mass.

Question 5

If a sample of water contains 11.2% hydrogen by mass, what is the percent by mass of oxygen in the same sample?

Accepted Answer

88.8%

Question 6

A student claims to have synthesized a new compound with the formula H2O, but the mass ratio of hydrogen to oxygen is 1:4. Which law does this claim violate?

Accepted Answer

Law of Definite Proportions

Question 7

In the decomposition of water ($$2	ext{H}_2	ext{O} ightarrow 2	ext{H}_2 + 	ext{O}_2$$), how many oxygen atoms are present on each side of the equation?

Accepted Answer

2 on the left, 2 on the right

Question 8

Which historical figure is credited with establishing the Law of Conservation of Mass?

Accepted Answer

Antoine Lavoisier

Question 9

A compound is found to contain 24.0 g of carbon and 32.0 g of oxygen. What is the mass ratio of carbon to oxygen in this compound?

Accepted Answer

3:4

Question 10

Which of the following scenarios would violate the Law of Conservation of Mass if it were observed?

Accepted Answer

A sealed container of reacting chemicals loses mass after the reaction.

Question 11

If 18.02 g of water is decomposed, how many grams of hydrogen are produced, given that water is 11.2% hydrogen by mass?

Accepted Answer

2.02 g

Question 12

Which of the following best describes the relationship between the number and types of atoms in the reactants and products of a chemical reaction?

Accepted Answer

The number and types of atoms are always the same on both sides of a balanced chemical equation.

Question 13

A sample of a compound contains 4.04 g of hydrogen and 32.00 g of oxygen. Is this compound water? Use the Law of Definite Proportions to justify your answer.

Accepted Answer

Yes, because the mass ratio of H:O is 1:8, which matches water.

Question 14

Which of the following statements is NOT a direct implication of the Law of Conservation of Mass?

Accepted Answer

The ratio of elements in a compound can vary depending on the reaction conditions.

Question 15

Which of the following best explains why the decomposition of water always produces hydrogen and oxygen in a 2:1 molar ratio?

Accepted Answer

Because the Law of Definite Proportions dictates a fixed ratio of hydrogen to oxygen atoms in water.

Fundamental Chemical Laws: Atoms, Molecules, and Ions

Study Guide - Practice Questions

Study Guide - Flashcards