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9.3 Notes. Learning Targets  Given the quantities of reactants in a chemical reaction, determine the limiting and excess reactants.

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Presentation on theme: "9.3 Notes. Learning Targets  Given the quantities of reactants in a chemical reaction, determine the limiting and excess reactants."— Presentation transcript:

1 9.3 Notes

2 Learning Targets  Given the quantities of reactants in a chemical reaction, determine the limiting and excess reactants

3 What is a Limiting Reagent?  The coefficients in balanced chemical equations indicate the amount of each substance available to react N 2(g) + 3H 2(g) → 2NH 3(g)  In this balanced equation one molecule of N 2 reacts with three molecules of H 2, producing two molecules of NH 3  What would happen if two molecules of N 2 reacted with three molecules of H 2 ?

4 2N 2(g) + 3H 2(g) → 2NH 3(g)  Before the reaction takes place, nitrogen and hydrogen are present in a 2:3 ratio. One molecule of N 2 will react with three molecules of H 2, to produce two molecules of NH 3 At this point, all of the hydrogen has been used up and the reaction stops One molecule of unreacted nitrogen will remain

5 Limiting vs. Excess Reagents  In this scenario, hydrogen would be considered the limiting reagent The limiting reagent limits the amount of product that can be formed in a reaction The reaction occurs until the limiting reagent is used up

6  In contrast, the reactant that is not completely used up is called the excess reagent In this example, nitrogen is the excess reagent

7 Sample Problems  Sodium chloride can be prepared by the reaction of sodium metal with chlorine gas. 2Na +Cl 2 → 2NaCl  Suppose that 6.70 mol Na reacts with 3.20 mol Cl 2 ○ What is the limiting reactant? Cl 2 ○ How many moles of NaCl are produced? 6.4 moles NaCl

8  The equation for the complete combustion of ethane (C 2 H 4 ) is C 2 H 4 + 3O 2 → 2CO 2 +2H 2 O  If 2.70 mols C 2 H 4 is reacted with 6.30 mols O 2, ○ Identify the limiting reagent. Oxygen (O 2 ) ○ Calculate the moles of water produced 4.2 moles

9  The properties of copper (I) sulfide are very different from the properties of the elements copper and sulfur 2Cu + S → Cu 2 S ○ What is the limiting reagent when 80.0 g Cu reacts with 25.0 g S? Copper (Cu) ○ What is the maximum number of grams of Cu 2 S that can be formed? g

10  Hydrogen gas can be produced in the laboratory by the reaction of magnesium metal with hydrochloric acid Mg + 2HCl → MgCl 2 + H 2 ○ Identify the limiting reagent when 6.00 g HCl reacts with 5.00 g Mg HCl ○ What is the maximum number of grams of H 2 that can be formed? 0.16 g HCl


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