RPAL Conservation of Mass 2

Question 1

In the reaction N₂ + 3H₂ → 2NH₃, if 28 g of N₂ reacts with 6 g of H₂, what mass of NH₃ is produced?

Accepted Answer

34 g

Answer

By conservation of mass, 28 g N₂ + 6 g H₂ = 34 g NH₃, since all reactants are consumed and mass is conserved.

Question 2

Which quantity is always equal before and after a chemical reaction in a closed system?

Accepted Answer

Total mass

Answer

Total mass is always conserved in a closed system because atoms are merely rearranged, not created or destroyed.

Question 3

A reaction produces 18 g of water and 44 g of CO₂ from methane and oxygen. If 16 g of methane was used, how much oxygen was consumed?

Accepted Answer

46 g

Answer

Total product mass = 18 + 44 = 62 g; mass of O₂ = 62 g − 16 g (CH₄) = 46 g.

Question 4

Conservation of mass requires that a chemical equation must be:

Accepted Answer

Balanced

Answer

A balanced equation ensures that the number of each type of atom is equal on both sides, reflecting conservation of mass.

Question 5

If 50 g of reactants are placed in a sealed, rigid container and a reaction occurs, what is the mass of the products?

Accepted Answer

Exactly 50 g

Answer

In a sealed system, conservation of mass guarantees the total mass of products equals the total mass of reactants, which is 50 g.

RPAL - Reactants, Products, and Leftovers Practice Test