Title: Lesson 7 Limiting Reagent and Mass of Product Learning Objectives:

1. Understand what limiting reagent is and how it affects mass of product

•

Preparation of Silver Chromate

In this experiment you will prepare silver chromate • The challenge is that you will start with an unknown mixture of the reactants and will have to use your knowledge of stoichiometry to work out its composition

• Use the idea of limiting reactants to identify the limiting reactant and solve Mg + 2 HCl –  MgCl 2 the problem.

+ H 2 0.15 mol Mg reacting with 0.25 mol HCl. How many moles of H 2 is formed?

• 2 C – 2 H 6 + 10 O 2  0.55 mol C 2 H 6 4 CO 2 + 6 H 2 O reacting with 3.50 mol O 2 . How many moles of CO 2 is formed?

• 3 Pb(NO 3 ) 2 – + 2 AlCl 3  2 Al(NO 3 ) 3 + 3 PbCl 2 2.60 mol Pb(NO 3 ) 2 reacting with 3.00 mol AlCl 3 . Which reactant is in excess and how much remains after the reaction?

• Ba – 3 N 2 + 6 H 2 O  3 Ba(OH) 2 + 2 NH 3 1.45 mol Ba 3 N 2 reacting with 10.0 mol H 2 O. Which reactant is present in excess and how much remains after the reaction?

• •

Determining Theoretical Yield

The theoretical yield is the amount of product you expect to make if all of your limiting reactant fully reacts.

It can be calculated by following these steps: Calculate moles of all reactants Determine limiting reactant Use mole ratios to calculate moles of product expected • Convert moles of product to mass/volume/solution etc.

All this does is string together all the calculations you have already met.

Some problems – Theoretical Yield

• Have a go at the problems found here .