1. STOICHIOMETRY Mass relationship of reactants and products in a chemical reaction
Hydrogen gas + nitrogen gas ----> ammonia gas
Qualitative: describes the “nature” of the reactants and products
Quantitative: describes the amounts of reactants and products

2. Steps for solving Stoichiometry problems:
Write a balanced equation for the question.
Understand the mole and molar ratio
Convert mass of reactant to moles of reactant.
Convert moles of reactant to moles of product.
Convert moles of product to grams of product.
Pick up the calculator and do the math!!

3. How about something a little easier to follow???? Like………….
FOOD!!!!!

4. The Stoichiometry of a sandwich…..
The SMCHS famous sandwich consists of 2 slices of bread, 2 slices of deli meat, 1 slice of cheese, and 3 slices of pickle.
Write an equation for the recipe…...
2 slices bread + 2 slices meat + 1 slice cheese + 3 slices pickle sandwich
OR…..
2B + 2M + 1C + 3P B2M2CP3

5. EVALUATION: WE CAN MAKE 4 COMPLETE SANDWICHES!!
How many SMCHS famous sandwiches can be produced when 8 slices of bread, 8 slices of meat, 4 slices of cheese, and 12 slices of pickles are available?
Break it down…..
BREAD: 8B = 4 B2M2CP3
MEAT: M = 4 B2M2CP3
CHEESE: 4C = 4 B2M2CP3
PICKLES: 12P = 4 B2M2CP3
EVALUATION: WE CAN MAKE 4 COMPLETE SANDWICHES!!

6. How many of each ingredient is needed to make 10 SMCHS famous sandwiches?
BREAK IT DOWN…..
BREAD: 10B2M2CP3 x (2B / B2M2CP3 )= 20B
MEAT: 10B2M2CP3 x (2M / B2M2CP3 )= 20M
CHEESE: 10B2M2CP3 x (1C / B2M2CP3 )= 10C
PICKLES: 10B2M2CP3 x (3P / B2M2CP3 )= 30P
THUS: 10 Sandwiches require 20B, 20M, 10C, and 30P

7. But what if you ran out of pickles?
Pickles would be the LIMITING REAGENT for the sandwiches
In any reaction you will likely have a limiting reagent AND an excess reagent.
Too little of one
Too much of the other

8. 3 H2 + 1 N2 2NH3 What do the coefficients mean?
3 molecules : 1 molecule : 2 molecules
OR 3 moles : 1 mole : 2 moles

9. 1N2 + 3H2 2NH3
1 molecules : 3 molecules : 2 molecules
10 molecules : 30 molecules : 20 molecules
100 molecules : 300 molecules : 200 molecules
1 (6x1023) : 3 (6x1023) : 2 (6x1023)
1 MOLE : 3 MOLE : 2 MOLE

10. allowing you to solve problems dealing with masses of substances!
1N2 + 3H2 2NH3
1mole of : 3mole of : 2mole of
N2 molecules H2 molecules NH3 molecules
This is the MOLAR RATIO
allowing you to solve problems dealing with masses of substances!

11. 1 N2 + 3 H2 2 NH3 If 75g of hydrogen reacts,
A) How many g of N2 reacts?
Use the molar ratio!!
First convert the grams to moles……
75g H2 x 1moleH2 / 2.02g H2

12. Next use molar ratio….. 75g H2 x 1mole x 1mole N2 2.02g H2 3mole H2
Now you’ve converted to moles of N2, make the final conversion into grams!!!
75g H2 x 1mole x 1mole N2 x 28g N2
2.02g H mole H mole N2

13. 75g H2 x 1mole H2 x 1mole N2 x 28g N2 2.02g H2 3mole H2 1mole N2
= 346.5g = 350g of N2

14. 1 N2 + 3 H2 2 NH3 If 75g of hydrogen reacts, B) How many g of NH3 are formed?
75g H2 x 1mole H2 x 2mole NH 3 x g NH3
2.02g H mole H mole NH3
MOLAR RATIO:
3mole H2 : 1mole N2 : 2mole NH 3
= 420g NH3

15. Use the same system for these
Mass - Volume Stoichiometry
Instead of converting the moles of unknown to grams you convert to volume (L)
Volume - Volume - Stoichiometry
Instead of using the molar ratio you use volume ratio and solve for volume
Rules remain the same.
Just use these differences and when dealing with mass of gas STP comes in