Chapter 9

1. Chapter 9 Stoichiometry

2. Stoichiometry • Stoy-key-ah-met-tree • Mole ratio with reaction coefficients • (aka the big numbers you used to balance equations mean the number of moles of each element/compound) • Like recipes, you can double, half, triple, etc.

3. Molar conversions • To convert from moles of one substance to another, divide by coefficient of what you’re given and moletiply by what you need to find. • See examples on board and p. 305

4. Gram conversions • To convert between grams of two substances, divide, divide, times, times • Divide by the mass of the known amount of substance, then divide by the coefficient of that known substance • Multiply by the coefficient in front of what you’re looking for, then multiply by the mass of what you’re looking for • See examples on board and p. 309

5. Limiting Reactants + Excess • You will be given gram amounts or molar amounts of both reactants in an equation. • You may need to pick a product to compare them to (find the moles or grams of product, like before) • See which reactant makes less product (like 20 bread + 20 fillings makes 10, not 20 sandwiches)- that is the limiting reactant • Either subtract your two answers or compare the reactants and subtract from the original to get the excess (See examples on board or p. 313)

6. % yield • % yield = actual/theoretical x 100% • Actual- what found in lab • Theoretical- what calculated on paper (like problems we’ve done • Why very rarely 100%? What causes 0% • See examples on board, and p. 317