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What is the molar mass for Calcium hydroxide?

A.57.08 g/mol

B. 74.08 g/mol

C. 64.08 g/mol

D. 27 g/mol

Stoichiometry

- The molar relationship between all of the compounds in a balanced equation.
- Law of Conservation of Mass
- What is on the left (reactant side) must equal what is on the right (product side).

- What is a molar ratio?
- The ratio is represented by the coefficient in front of the chemical formula.
- In stoichiometry, a molar ratio is the small, whole number ratio between each of the participants in a chemical reaction.
1N2 + 3H2 2NH3

The ratio of Nitrogen to Hydrogen to Ammonia is 1:3:2

- Step 1: Write out the equation.
- Step 2: Balance the equation.
- Step 3: Determine the molar relationships

Example

- Write and balance the equation for the reaction of Calcium hydroxide and Ammonium sulfate yields Calcium sulfate and ammonia and water.
- What is the mole ratio between each of the participants?

- Write out the equation.
- Ca(OH)2(aq)+ (NH4)2SO4(aq) → CaSO4 + NH3(g) + H2O(l)

- Balance the Equation
- Ca(OH)2(aq)+ (NH4)2SO4(aq) → CaSO4 + 2NH3(g) + 2H2O(l)

- Determine the molar relationships
- 1:1:1:2:2

- Write and balance the reaction of sodium with water to yield sodium hydroxide and hydrogen gas.
- What are the ratios?
- 2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g)
- The ratio is 2:2:2:1

- Write and balance the equation for the reaction of ammonia with oxygen to yield nitric acid (HNO3) and water.
- NH3(g) + 2O2(g) → HNO3(aq) + H2O(l)
- The ratio is 1:2:1:1

- Stoichiometry means that if you know one piece of information about ONE compound in an equation, you can determine EVERYTHING else!!!!!
- If you have 3L of Nitrogen, how many liters of ammonia will you produce?
N2 + 3H2 2NH3

- Let’s look at that last reaction again.
- N2(g) + 3H2(g) 2NH3(g)

- If you start out with 1 mole of Nitrogen gas and 3 moles of Hydrogen gas, you will make 2 moles of Ammonia gas.
- It is important in industry to know the exact proportions of your ingredients so that you will not have excess waste in your product.

1. Write the balanced equation

17.0g

?g

AgNO3 + NaCl AgCl + NaNO3

2. Given and asked for

3. Moles of given

17.0g AgNO3 x 1 mol =

170 g

0.100 mol AgNO3

AgNO3 + NaCl AgCl + NaNO3

4. Moles asked for

0.100 mols AgNO3 x 1 mol AgCl =

1 mol AgNO3

0.100 mol AgCl

5. Convert your answer

0.100 mol AgCl x 144 g AgCl =

1 mol AgCl

14.4 g AgCl

How many grams of calcium hydroxide will be needed to react completely with 10.0 g of phosphoric acid (H3PO4) in a double displacement reaction?

1. Balanced equation

? g

10.0 g

3Ca(OH)2 + 2H3PO4 Ca3(PO4)2 + 6HOH

2. Given & asked for

3. Mols given

10.0 g H3PO4 x 1mol H3PO4 =

98.0 g

0.102 mol H3PO4

4. Mols asked for

0.102 mol H3PO4 x 3 mol Ca(OH)2 =

2 mol H3PO4

0.153 mol Ca(OH)2

5. Convert answer

0.153 mol Ca(OH)2 x 74 g =

1 mol Ca(OH)2

11.3 g Ca(OH)2

What mass of sodium oxide is produced by the reaction of 1.44 g of sodium with oxygen?

4Na + O2 2Na2O

1.44g ?g

1.44g x 1mol / 23g = 0.0626mol Na

0.0626mol Na x 2Na2O / 4Na = 0.0313mol Na2O

0.0313mol Na2O x 62g / 1mol = 1.94g Na2O

How many kg of lead (II) nitrate will be needed to react with sodium chromate to produce 4.62 kg of lead (II) chromate?

Pb(NO3)2 + Na2CrO4 2NaNO3 + PbCrO4

?kg4620g (4.62kg)

4620g x 1mol / 323g = 14.3mol PbCrO4

14.3mol PbCrO4 x 1mol / 1mol = 14.3mol Pb(NO3)2

14.3mol Pb(NO3)2 x 331g / 1mol = 4730g(4.73kg)Pb(NO3)2

What quantity of hydrogen gas is formed when 0.85 g of lithium reacts with water? How much lithium hydroxide is produced?

2Li + 2H2O 2LiOH + H2

0.85g?g

0.85g Li x 1mol / 7g = 0.12molLi

0.12mol Li x 1H2 / 2Li = 0.060molH2

0.060mol H2 x 2g / 1mol = 0.12g H2 3.0g LiOH

What mass of water is given off when 192 kg of C7H14 burn completely in air? How much oxygen is used?

2C7H14 + 21O2 14CO2 + 14H2O

192,000g (192kg)?g

192,000g C7H14 x 1mol / 98g = 1960mol C7H14

1960mol C7H14 x 14mol / 2mol = 13700mol H2O

13700mol H2Ox 18g / 1mol = 247,000g H2O 658,000g O2

- P. 307, #1-4
- Fe2O3 + 2Al 2Fe + Al2O3

- P. 309, #1-4

- P. 311, #1-7