1. CONSERVATION OF MASS

2. REVIEW
Chemical equations consist of reactants and products
Matter can be neither created nor destroyed
2 H2 + O H2O
Reactants Products

3. …the mass of the reactants is always equal to the mass
Law of Conservation of Matter
…the mass of the reactants
is always equal to the mass
of the products
Example
Reactants Products
2H2 + O H2O
2g g = g
18g = g

4. Example # 1 REMEMBER... 29 g + O2 = 88 g + 48 29 g + O2 = 136 g
In a chemical reaction below, how many grams of oxygen (O2) was used given the following information.
29g ? g g
REMEMBER...
mass of reactants = mass of products
29 g + O2 = 88 g + 48
29 g + O2 = 136 g
O2 = 107 grams

5. 2 H2O  2 H2 + O2 Example # 2 2 H2O  2 H2 + O2 9 g = ? + 8 g
Water (H2O) can be broken down into hydrogen and oxygen.
During a reaction you notice that 9 grams of water will produce 8 grams of oxygen (O2) and a certain amount of hydrogen (H2). How much hydrogen is produced?
2 H2O  2 H2 + O2
2 H2O  2 H2 + O2
9 g = ? g
H2 = 1 grams

6. Example # 3 H2SO4+ Ca(OH)2  CaSO4 + 2H2O 37 g + Ca(OH)2 = 51 g + 14 g
37 grams sulphuric acid (H2SO4) is neutralized with calcium hydroxide (Ca(OH)2).
During the reaction, calcium sulphate (CaSO4), a salt, and water are produced. If 14g of water & 51g of salt are produced, how much calcium hydroxide was initially used?
H2SO4+ Ca(OH)2  CaSO4 + 2H2O
37 g + Ca(OH)2 = g g
37 g + Ca(OH)2 = 65 g
Ca(OH)2 = 28 grams

7. KEY POINTS
Conservation of matter states the mass of the reactants will equal the mass of the products.
MASS OF REACTANTS = MASS OF PRODUCTS

8. PRACTICE PROBLEMS
Study guide, Module 3, page 36
Worksheet # 10