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Limiting and Excess Reactants. LIMITING REACTANTS LIMIT HOW MUCH OF THE PRODUCT CAN ACTUALLY BE PRODUCED DURING THE REACTION.

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Presentation on theme: "Limiting and Excess Reactants. LIMITING REACTANTS LIMIT HOW MUCH OF THE PRODUCT CAN ACTUALLY BE PRODUCED DURING THE REACTION."— Presentation transcript:

1 Limiting and Excess Reactants

2 LIMITING REACTANTS LIMIT HOW MUCH OF THE PRODUCT CAN ACTUALLY BE PRODUCED DURING THE REACTION

3 EXCESS REACTANTS The reactants that are left over when the reaction stops. *When all the limiting reactant is used up

4 How to find the limiting reactants 1. Solve each of the problems 2. Which of the problems produces the least amount? 0 This is your Limiting Reactant

5 Finding the limiting reactants NaOH + HCl ⇒ H 2 O + NaCl If there are 25 grams of NaOH, how many grams of H 2 O will be formed? If there are 16 grams of HCl, how many grams of H 2 O will be formed? Which is the limiting reactant?______________________

6 Finding the limiting reactant 2H 2 + O 2 ⇒ 2H 2 O Determine the limiting reactant and how much water will be formed from it, if the following is true: 3 grams of H 2 and 5 grams of O 2

7 Percent Yield

8 0 This is a measurement of the accuracy of the chemical reaction. 0 Actual Yield: is the amount of product actually produced, and measured at the end of the reaction. 0 Theoretical Yield: (expected value) is how much product was expected to be produced. This is done by calculating how much should be produced based on the amounts of beginning products. Actual Yield Theoretical Yield x 100 = Percent Yield

9 How to determine the % yield: 1. Complete the conversions of both givens 2. Determine which substance is the limiting reactant 3. Use the limiting reactant as the theoretical yield 4. Calculate the percent yield 1. Divide the actual yield by the theoretical yield 2. Multiply by 100 *This determines how accurate your reaction was in percentage

10 Determining the % Yield: Mg(OH) 2 + 2NaCl ⇒ 2NaOH + MgCl 2 Determine the limiting reactant and how many grams of MgCl 2 will be formed from it, if there are 4.6 grams of Mg(OH) 2 and 7.8 grams of NaCl. What is the % yield if only 5.78g of MgCl 2 was collected at the end of the experiment/reaction?

11 Determining the % Yield: 2H 2 + O 2 ⇒ 2H 2 O Determine the limiting reactant and how much water should be formed from it, if 3 grams of H 2 and 5 grams of O 2. 3g H 2 1 mol H 2 2 mols H 2 O 18g H 2 O = 27g H 2 O 2g H 2 2 mols H 2 1 mol H 2 O 5g O 2 1 mol O 2 2 mols H 2 O 18g H 2 O = 5.625g H 2 O 32g O 2 1 mol O 2 1 mol H 2 O What is the percent yield, if the chemist only gathers 3.78g of H 2 O at the end of the reaction?


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