1. Stoichiometry
Stoichiometry is a fancy chemistry word meaning “to calculate quantities in a chemical reaction”.
Or in other words, if I mix this much of “X” and this much of “Y” they will react to form this much of “Z”.

2. Set Up of Stoich Problems
In most stoichiometry problems we are using a known mass and the balanced equation coefficients to determine the mass of an unknown

3. Mole Ratios!!!!
Keep in mind that the coefficients in the balanced equation are mole ratios, NOT mass ratios (this means you have to get things into moles first)

4. Steps to Solving Stoich. Problems
Write and balance the chemical equation
Convert the mass of the known chemical to moles
(mass/molar mass) = moles
Use the mole ratio to find moles of unknown chemical(s).
4. Convert moles of unknown chemical to mass
moles x molar mass = mass

5. Caveat
Just a note…
A common question is – “do you include the balancing coefficient in the molar mass?”
The answer is – NO! You need to use the subscripts in the molar mass, but NOT the balancing coefficients!

6. Example #1
A strip of zinc metal with a mass of 2.00 g is placed in an aqueous solution containing 2.50 g of silver nitrate. How many grams of silver will form?
Step 1: Write and balance the chemical equation
Zn (s) + 2 AgNO3 (aq)  2 Ag (s) + Zn(NO3)2 (aq)

7. Example #1- Step 2
A strip of zinc metal with a mass of 2.00 g is placed in an aqueous solution of silver nitrate. How many grams of silver will form?
Step 2: Convert the mass of the known chemical to moles
(mass/molar mass) = moles

8. Example #1-Step 3 Zn (s) + 2 AgNO3 (aq)  2 Ag (s) + Zn(NO3)2 (aq)
Step 3: Use the coefficients of the balanced equation to determine the mole ratios.

9. Example #1-Step 5 Step 5: Convert moles of unknown chemical to mass
moles x molar mass = mass

10. Example #1-Step 2
A strip of zinc metal with a mass of 2.00 g is placed in an aqueous solution containing 2.50 g of silver nitrate. How many grams of silver will form?
Step 2: Convert the mass of the known chemical to moles
(mass/molar mass) = moles

11. Example #1-Step 3 Zn (s) + 2 AgNO3 (aq)  2 Ag (s) + Zn(NO3)2 (aq)
Step 3: Determine limiting reagent (limiting reagent is the reagent that doesn’t fulfill the mole ratio of the balanced equation). Use the coefficients of the balanced equation to determine the mole ratios.
Limiting Reagent

12. Example #1-Step 4
Use the mole ratio to find moles of unknown chemical(s). You MUST use the moles of the limiting reagent to determine the moles of the unknown.

13. Example #1-Step 5 Step 5: Convert moles of unknown chemical to mass
moles x molar mass = mass

14. Stoichiometry Steps Write and balance the chemical equation
Convert the mass of the known chemical to moles
(mass/molar mass) = moles
Determine limiting reagent (limiting reagent is the reagent that doesn’t fulfill the mole ratio of the balanced equation). Use the coefficients of the balanced equation to determine the mole ratios.

15. Stoichiometry
Use the mole ratio to find moles of unknown chemical(s). You MUST use the moles of the limiting reagent to determine the moles of the unknown.
Convert moles of unknown chemical to mass
moles x molar mass = mass
Repeat if necessary for other chemicals
Just a note…
A common question is – “do you include the balancing coefficient in the molar mass?” The answer is – NO! You need to use the subscripts in the molar mass, but NOT the balancing coefficients!