Start-Up

What is the molar mass for Calcium hydroxide?A. 57.08 g/molB. 74.08 g/molC. 64.08 g/molD. 27 g/mol

Stoichiometry

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).

Ratio

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

Steps for Determining Molar Ratio

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

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?

Example

The Step-by-Step Process

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

Another example

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

Now try this one

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

The Key

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

Think of it as a recipe

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.

How many grams of silver chloride can be produced from the reaction of 17.0 g

silver nitrate with excess sodium chloride solution?

1. Write the balanced equation

AgNO3 + NaCl AgCl + NaNO3

2. Given and asked for

17.0g ?g

3. Moles of given

17.0g AgNO3 x 1 mol = 170 g

0.100 mol AgNO3

Mass-Mass Problem Cont.

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 AgCl14.4 g AgCl

AgNO3 + NaCl AgCl + NaNO3

Example #2

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

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

2. Given & asked for

10.0 g? g

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 answer0.153 mol Ca(OH)2 x 74 g = 1 mol Ca(OH)2

11.3 g Ca(OH)2

4Na + O2 2Na2O1.44g ?g

1.44g x 1mol / 23g = 0.0626mol Na0.0626mol Na x 2Na2O / 4Na = 0.0313mol Na2O0.0313mol Na2O x 62g / 1mol = 1.94g Na1.94g Na22OOHow 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

?kg 4620g (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)(4.73kg) Pb(NOPb(NO33))22

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

2Li + 2H2O 2LiOH + H2

0.85g ?g0.85g Li x 1mol / 7g = 0.12mol Li0.12mol Li x 1H2 / 2Li = 0.060mol H2

0.060mol H2 x 2g / 1mol = 0.12g H0.12g H22 3.0g 3.0g LiOH 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) ?g192,000g C7H14 x 1mol / 98g = 1960mol C7H14

1960mol C7H14 x 14mol / 2mol = 13700mol H2O13700mol H2Ox 18g / 1mol = 247,000g H247,000g H22O O 658,000g O658,000g O22

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

Classwork

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

P. 309, #1-4

Homework

P. 311, #1-7