RPAL Conservation of Mass

Question 1

Which law states that matter is neither created nor destroyed in a chemical reaction?

Accepted Answer

Law of Conservation of Mass

Answer

The Law of Conservation of Mass states that the total mass of reactants equals the total mass of products in a chemical reaction.

Question 2

In a sealed container, 10 g of reactant A reacts completely with 5 g of reactant B. What is the total mass of products formed?

Accepted Answer

15 g

Answer

By conservation of mass, the total mass of products equals the total mass of reactants: 10 g + 5 g = 15 g.

Question 3

A balanced chemical equation demonstrates conservation of mass because:

Accepted Answer

It has the same number of atoms of each element on both sides

Answer

A balanced equation has equal numbers of each type of atom on both sides, ensuring mass is conserved since atoms are not created or destroyed.

Question 4

If 4 g of hydrogen reacts with 32 g of oxygen to form water, what mass of water is produced?

Accepted Answer

36 g

Answer

By conservation of mass, 4 g H₂ + 32 g O₂ = 36 g H₂O, since total reactant mass equals total product mass.

Question 5

Which of the following best describes what happens to atoms during a chemical reaction?

Accepted Answer

Atoms are rearranged to form new substances

Answer

In chemical reactions, atoms are rearranged — bonds are broken and formed — but atoms themselves are neither created nor destroyed.

RPAL - Reactants, Products, and Leftovers Practice Test