Conservation of Mass in Chemistry

What does the conservation of mass principle state about chemical reactions?

• Mass is always lost in chemical reactions.

• Atoms are created and destroyed in chemical reactions.

• Mass is always conserved in chemical reactions.

• Chemical reactions do not involve any change in bonds.

In the reaction between sodium and chlorine to form sodium chloride, why do we need two sodium atoms for every chlorine molecule?

• Because sodium is a gas and chlorine is a solid.

• Because sodium and chlorine have the same atomic mass.

• Because each chlorine molecule contains two chlorine atoms.

• Because sodium is heavier than chlorine.

Why might the mass appear to change in a reaction involving gases?

• Because gases are not part of the conservation of mass principle.

• Because gases are heavier than solids.

• Because gases can come from or escape into the air, affecting measurements.

• Because gases do not react with solids.

What happens to the mass of magnesium when it reacts with oxygen to form magnesium oxide?

• The mass increases because oxygen from the air is added.

• The mass remains the same because no new atoms are formed.

• The mass decreases because magnesium is a gas.

• The mass decreases because oxygen is lost.

How can you ensure accurate mass measurements in reactions involving gases?

• By conducting the experiment in an open environment.

• By using a larger scale.

• By using a sealed container to trap all gases.

• By only measuring solid reactants and products.