Unit 5: Conservation of Mass

How many calcium (Ca) and oxygen (O) atoms are present?

• 4 calcium and 9 oxygen

• 4 calcium and 12 oxygen

• 4 calcium and 24 oxygen

• 8 calcium and 24 oxygen

Which are the reactants?

• H₂ (g) + O₂ (g)

• H₂O (g)

• H₂ only

• O₂ only

Why do we balance chemical equations?

• because Thanos said so...

• so the reaction will actually happen

• to follow the law of conservation of energy

• to follow the law of conservation of mass

Is this equation properly balanced?

• Yes!

• Almost, there should be a 3 in front of the CuCl₂

• Nope 😒

Why does this violate the law of conservation of mass?

• there is a different amount of hydrogen in the reactants and products

• there is a different amount of oxygen in the reactants and products

• there is a different amount of water in the reactants and products

• it is balanced 👍

Balance this equation:

• 2, 2, 8, 2

• 1, 1, 4, 1

• 2, 3, 4, 5

• it is already balanced 👍

Identify the type of reaction:

A + BC → AC + B

• synthesis

• decomposition

• single replacement

• double replacement

• combustion

Identify the reaction type:

• synthesis

• decomposition

• single replacement

• double replacement

• combustion

Identify the reaction type:

2 Al + 3 S → Al₂S₃

• synthesis

• decomposition

• single replacement

• double replacement

• combustion

Identify the reaction type:

C₃H₈ + 5 O₂ → 3 CO₂ + 4 H₂O

• synthesis

• decomposition

• single replacement

• double replacement

• combustion