WE BE COOKING….

Stoichiometry

Stoichiometry

Deals with the chemistry of quantifying chemical reactions through the use of: Balancing equations Moles (mol) Molarity (mol/L) Mass (grams)

Cooking…

A recipe is used to make a dish…let’s say brownies

½ cup butter2 oz of chocolate1 cp sugar2 eggs1 tsp vanilla2/3 cp flour½ tsp baking powder¼ tsp salt

24 Brownies

What if I want 36 Brownies

The ingredients don’t change but the amount does proportionally…

½ cup butter2 oz of chocolate1 cp sugar2 eggs1 tsp vanilla2/3 cp flour½ tsp baking powder¼ tsp salt

¾ cup butter3 oz of chocolate1.5 cp sugar3 eggs1.5 tsp vanilla1 cp flour¾ tsp baking powder1/8 tsp salt

x by 1.5

Recipes are just like chemical equations

2Mg(s) + O2(g) 2MgO(s)

2 mol of Mg + 1 mol of O2 yields 2 moles of MgO

If I want 6 moles of MgO…I need 6 mol of Mg and 3 moles of O2.

Proportions…Wait…wait…proportion? That means

conversion!!What…DA?

Coefficients are Conversion Factors

2KClO3(s) 2KCl(s) + 3O2(g)

Conversions:2 mol KClO3 = 2 mol KCl

2 mol KClO3 = 3 mol O2

2 mol KCl = 3 mol O2

Question:How many moles of oxygen gas is produced if there is 4.56 moles of KClO3 present?

4.56 mol KClO3 mol KClO3

mol O23

2

Coefficients from balanced equation

= 6.84 mol of O2

So what does this mean…

From previous knowledge: Liters to moles (Molarity) Mass to moles (molar mass)

Now… Moles to moles (using coefficients)

We can not only work with one particular compound/molecule/atom…now we can work with multiple compounds/molecules/atoms

All aboard to moleland!!

Let’s put this knowledge into action..

2KClO3(s) 2KCl(s) + 3O2(g)

How many grams of KCl is produced if 6.89 grams of KClO3 are decomposed?

6.89 g KClO3

g of KClO3

mol of KClO3

122.55

Molar mass of KClO3

1

mol KClO3

mol KCl2

2 1 mol of KCl

74.55 g of KCl

Molar mass of KCl

= 4.19 g of KCl

Coefficients

Review Steps for Stoiching…

Write and balancing chemical reactionStart with given (mass, moles, or volume)Convert to moles (if mass and volume is

given) Moleland!!

Convert to moles of another compound/atomConvert to final unit (moles/grams/volume)

0.100 mol AgNO3

Working with molarity

Cu(s) + 2AgNO3(aq) 2Ag(s) + Cu(NO3)2(aq)

How many grams of copper will be required to completely replace silver from 208 mL of 0.100 M solution of AgNO3?

208 mL 1 mol Cu

1000 mL

1 L

2 mol AgNO3 1 mol Cu

63.546 g Cu

Molar mass of Cu

= 0.661 g of Cu

Coefficients

1 L

Reasons for Stoichiometry

Quantify how much you need to start with Without throwing in any amount willy nilly

Quantify how much you make Determine how baller you are

Quantify how much you have left over

Lead(II) nitrate solution reacts with 27.5 mL of 3.00 M carbonic acid, H2CO3(aq), how many grams of

lead(II) carbonate is produced?

3.00 mol H2CO3

More Practice

27.5 mL 1 mol PbCO3

1000 mL

1 L

1 mol H2CO3 1 mol PbCO3

267.21 g PbCO3

Molar mass of PbCO3

= 22.0 g of PbCO3

Coefficients

1 L

Pb(NO3)2(aq) + H2CO3(aq) PbCO3(s) + 2HNO3(aq)

Solid limestone, calcium carbonate, is heated to produced solid CaO and carbon dioxide gas. How

much limestone is required to produce 10.0 grams of calcium oxide?

1 mol CaO

More Practice

10.0 g CaO 1 mol CaCO3

1 mol CaO 1 mol CaCO3

100.085 g CaCO3

Molar mass of CaCO3

= 17.8 g of CaCO3

Coefficients

56.077 g CaO

CaCO3 CaO(s) + CO2(g)

Molar mass of CaO