•STUDY GROUPS- FIRST MEETING THIS WEEK

•EXAM #1 THIS WEEK! FRIDAY, SEPTEMBER 18TH

•Addition to Study Guide:

Given the masses of two reactants and a chemical equation, be able to determine e which is the limiting reactant

(Chemical Analysis is not on the exam)

Announcements

Alum Lab- % Yield Calculation

Limiting Reactants

2H2 + O2 2H2O

Example: We have 10 mol H2 and 7 mol O2

What is the number of moles of O2 needed to react with all of the H2?

How much O2 will be left over?7 mol O2 available- 5 mol O2 needed= 2 mol O2

22

222 52

110 Omol

Hmol

OmolHmolOmol

Limiting Reactants

2H2 + O2 2H2O

Example: We have 10 mol H2 and 7 mol O2

Limiting Reactants

If given the amount of starting materials, how do I determine which is the limiting reactant?

Two approaches:1. Determine the theoretical yield from each2. Divide the # moles of each by its stoichiometric #(In both approaches, the smaller # is the limiting

reactant)

Example

The reaction:

We have 5.0 mol SO2, 4.o mol O2, and 10.0 mol H2O. Which is the limiting reactant?

What if I started with 5g SO2, 4g O2, and 10g H2O?

)(2)()()(2 42222 aqSOHlOHgOgSO

Stoichiometry- Limiting Reactants

100mL 0.1M HCl + coil of Mg in each flask Flask 1= 1.2g Mg Flask 2= 0.6g Mg Flask 3= 2.4g Mg

The reaction:

Which balloon inflates the most? Least?Does half the Mg mean half the H2?Does twice the Mg mean twice the H2?

222 HMgClHClMg