1. Section 3: Stoichiometry - Mole:Mole and Gram:Gram
Unit 6: Stoichiometry
Section 3: Stoichiometry - Mole:Mole and Gram:Gram

2. Stoichiometry
Branch of chemistry that involves using known ratios of products and reactants to determine unknown data in a chemical reaction
Chemists use stoichiometry conversions like cooks use cooking recipes
Ratio for these conversions can be found in the balanced equation!! (Coefficients!)

3. Mole-to-Mole Formula
When converting from moles of one substance to moles of another
“G” stands for “given” chemical
“U” stands for “unknown” chemical
Use the coefficient from the balanced equation
Use the coefficient from the balanced equation

4. Mole-to-Mole Problems
Ex-1: If you want to manufacture moles of ammonia (NH3), how many moles of hydrogen will you need?
H2 + N2 → NH3
Step 1: Balance the equation
3H2 + N2 → 2NH3

5. Mole-to-Mole Problems
Ex-1: If you want to manufacture 150 moles of ammonia (NH3), how many moles of hydrogen will you need?
3H2 + N2 → 2NH3
Step 2: Identify the “given” and “unknown” from the problem with units.
G: 150 mol NH3
U: # mol H2

6. Mole-to-Mole Problems
Ex-1: If you want to manufacture 150 moles of ammonia (NH3), how many moles of hydrogen will you need?
3H2 + N2 → 2NH3
G: 150 mol NH U: # mol H2
Step 3: Set up a conversion factor with given units in the bottom:
150 mol NH3 x _______
mol NH3

7. Mole-to-Mole Problems
Ex-1: If you want to manufacture 150 moles of ammonia (NH3), how many moles of hydrogen will you need?
3H2 + N2 → 2NH3
G: 150 mol NH U: # mol H2
Step 4: The unit on top must be the unit you want; same as your “unknown”
150 mol NH3 x mol H2
mol NH3

8. Mole-to-Mole Problems
Ex-1: If you want to manufacture 150 moles of ammonia (NH3), how many moles of hydrogen will you need?
3H2 + N2 → 2NH3
G: 150 mol NH U: # mol H2
Step 5: Plug in the coefficients from the balanced equation:
150 mol NH3 x 3 mol H2 = 225 mol H2
2 mol NH3

9. Mole-to-Mole Problems
Ex-1: If you want to manufacture 150 moles of ammonia (NH3), how many moles of Hydrogen will you need?
3H2 + N2 → 2NH3
G: 150 mol NH U: # mol H2
Step 6: Round answer to the correct number of significant figures and include your unit!!!!
150 mol NH3 x 3 mol H2 = 225 mol H2 → 230 mol H2
2 mol NH3

10. Mole-to-Mole Practice
Ex-2: If you want to make 100 moles of ammonia (NH3), how many moles of Nitrogen (N2) will you need?
3H2 + N2 → 2NH3
50 mol N2

11. Mole-to-Mole Practice
Ex-3: If you have 36 moles of nitrogen (N2), how many moles of hydrogen (H2) will you need?
3H2 + N2 → 2NH3
110 mol H2

12. OMG ITS THE SAME AS THE MOLE TO MOLE FORMULA!
Gram-to-Gram Formula
Used to figure out the # of grams of one substance needed to make another
“U” = “unknown”; “G” = “given”
Use the coefficient from the balanced equation
OMG ITS THE SAME AS THE MOLE TO MOLE FORMULA!
Use the coefficient from the balanced equation

13. Gram-to-Gram Problems
Ex-1: How many grams of glass (SiO2) can be etched by 100 grams of hydrofluoric acid (HF)?
HF + SiO2 → SiF4 + H2O
Step 1: Balance the equation
4HF + SiO2 → SiF4 + 2H2O

14. Gram-to-Gram Problems
Ex-1: How many grams of glass (SiO2) can be etched by 100 grams of hydrofluoric acid (HF)?
4HF + SiO2 → SiF4 + 2H2O
Step 2: Identify the “given” and “unknown” from problem with units
G: 100 g HF
U: # g SiO2

15. Gram-to-Gram Problems
Ex-1: How many grams of glass (SiO2) can be etched by 100 grams of hydrofluoric acid (HF)?
4HF + SiO2 → SiF4 + 2H2O
Step 3: Set up a conversion factor with the given units in the bottom… this will be its molar mass. The numerator will always be 1 mole of the “given” chemical
100 g HF x 1 mol HF
g HF

16. Gram-to-Gram Problems
Ex-1: How many grams of glass (SiO2) can be etched by 100 grams of hydrofluoric acid (HF)?
4HF + SiO2 → SiF4 + 2H2O
Step 4: Next, use a mole-to-mole conversion factor to go from one chemical to the other. Take the numbers for the coefficients from the balanced equation.
100 g HF x 1 mol HF x 1 mol SiO2
g HF mol HF

17. Gram-to-Gram Problems
Ex-1: How many grams of glass (SiO2) can be etched by 100 grams of hydrofluoric acid (HF)?
4HF + SiO2 → SiF4 + 2H2O
Step 5: We need our answer in grams, so do a basic mole-to-gram conversion (1 mole on bottom; molar mass on top)
100 g HF x 1 mol HF x 1 mol SiO2 x g SiO2 =
g HF mol HF mol SiO2

18. Gram-to-Gram Problems
Ex-1: How many grams of glass (SiO2) can be etched by 100 grams of hydrofluoric acid (HF)?
4HF + SiO2 → SiF4 + 2H2O
Step 6: Make sure your final answer is in the correct # of sig figs with its unit
100 g HF x 1 mol HF x 1 mol SiO2 x g SiO2 =
g HF 4 mol HF mol SiO2
80 g SiO2

19. Gram-to-Gram Practice
Ex-2: How many grams of glass (SiO2) can be made from 230 grams of H2O?
4HF + SiO2 → SiF4 + 2H2O
380 g SiO2

20. Gram-to-Gram Practice
Ex-3: How many grams of Silicon fluoride (SiF4) are needed to make g of water?
4HF + SiO2 → SiF4 + 2H2O
g SiF4