Q: If a chemical reaction produces 17.0 grams of water from 5.0 grams of hydrogen and 12.0 grams of oxygen, which equation best represents the Law of Conservation of Mass?

$$\text{mass of reactants} = \text{mass of products}$$

Question 1

Which statement best describes the Law of Conservation of Mass?

Accepted Answer

The total mass of reactants equals the total mass of products in a chemical reaction.

Question 2

Given the reaction $$2H_2 + O_2$ \rightarrow 2H_2O$$, if you start with 10.0 grams of $$H_2$$ and 80.0 grams of $$O_2$$, what is the total mass of water produced?

Accepted Answer

$$90.0$$ grams

Question 3

In the reaction $$N_2 + 3H_2$$ \rightarrow 2NH_3$$, if 50.0 grams of H_2$ react with 25.0 grams of N_2$, what is the total mass of NH_3$ produced?

Accepted Answer

$$75.0$$ grams

Question 4

A student mixes 12.0 grams of hydrogen gas with 25.0 grams of oxygen gas to produce water. According to the Law of Conservation of Mass, what is the mass of water formed?

Accepted Answer

$$37.0$$ grams

Question 5

If 112.4 grams of calcium react with 24.0 grams of oxygen to form calcium oxide, what is the mass of calcium oxide produced?

Accepted Answer

$$136.4$$ grams

Question 6

Which of the following best explains why the mass of products equals the mass of reactants in a chemical reaction?

Accepted Answer

Atoms are rearranged but not created or destroyed.

Question 7

A chemical reaction occurs in a sealed container. If the total mass of reactants is 150 grams, but after the reaction the mass is measured as 145 grams, what is the most likely explanation?

Accepted Answer

Some product escaped from the container.

Question 8

In the reaction $$2H_2 + O_2$ \rightarrow 2H_2O$$, if you have 5.0 grams of $$H_2$$ and 40.0 grams of $$O_2$$, but only 42.0 grams of $$H_2O$$ are collected, what is the most likely reason for the discrepancy?

Accepted Answer

Some water vapor escaped during the reaction.

Question 9

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

Accepted Answer

Antoine Lavoisier

Question 10

A reaction between 20.0 grams of sodium and 30.0 grams of chlorine produces sodium chloride. What is the mass of sodium chloride formed?

Accepted Answer

$$50.0$$ grams

Question 11

If a chemical reaction produces 17.0 grams of water from 5.0 grams of hydrogen and 12.0 grams of oxygen, which equation best represents the Law of Conservation of Mass?

Accepted Answer

$$	ext{mass of reactants} = 	ext{mass of products}$$

Question 12

A scientist combines 40.0 grams of iron with 28.0 grams of sulfur to form iron(II) sulfide. What is the mass of iron(II) sulfide produced?

Accepted Answer

$$68.0$$ grams

Question 13

Which of the following is NOT a consequence of the Law of Conservation of Mass?

Accepted Answer

Mass is lost as heat during chemical reactions.

Question 14

In a closed system, 100 grams of reactants are used in a reaction. After the reaction, the products are weighed and found to be 100 grams. What does this demonstrate?

Accepted Answer

The Law of Conservation of Mass

Question 15

A reaction occurs in an open container and the mass of the products is less than the mass of the reactants. What is the most likely explanation?

Accepted Answer

A gas escaped from the container.

Law of Conservation of Mass and Chemical Reactions

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