Chemistry Unit 5 Worksheet 2: Limiting Reactants and ...

[Pages:2]Chemistry Unit 5 Worksheet 2: Limiting Reactants and Theoretical Yield

1.

Mg(s) + 2HCl(aq) MgCl2(aq) + H2(g)

You have 20g of Mg and 20g of HCl. Find the limiting reactant.

(a) Calculate the number of moles of each reactant you have been given in this question.

(b) (i) Using the mole ratios from the balanced chemical equation, how many moles of HCl is needed if you want all of the Mg to react?

(ii) Is 20g of HCl (= 0.5479 mol of HCl) enough HCl to react with all of the Mg? Yes/No _________ is the limiting reactant and _________ is present in excess.

(c) (i) Using the mole ratios from the balanced chemical equation, how many moles of Mg is needed if you want all of the HCl to react?

(ii) Is 20g of Mg (= 0.823 mol of Mg) enough Mg to react with all of the HCl? Yes/No _________ is the limiting reactant and _________ is present in excess.

Quick Method: 1. Find number of moles of each reactant 2. Write the mole ratio from the balanced equation 3. Divide the # of moles by the coefficient in the balanced equation 4. The smaller answer is the limiting reactant

Mg 20g ? 24.3g/mol = 0.823 mol

1

0.823

HCl 20g ? 36.5g/mol = 0.5479 mol

2

0.27395 Limiting Reactant

2. At high temperatures, sulfur combines with iron to form the brown-black iron (II) sulfide: Fe (s) + S (l) FeS (s) In one experiment, 7.62 g of Fe are allowed to react with 8.67 g of S. (a) Calculate the number of moles of each reactant you have been given in this question.

(b) (i) Using the mole ratios from the balanced chemical equation, how many moles of Fe is needed if you want all of the S to react?

(ii) Is 7.62g of Fe enough to react with all of the S? Yes/No _________ is the limiting reactant and _________ is present in excess.

Quick Method:

Fe

S

1. Find number of moles of

each reactant

2. Write the mole ratio from

the balanced equation

3. Divide the # of moles by the

coefficient in the balanced

equation

4. The smaller answer is the

limiting reactant

3. Methanol, CH3OH, which is used as a fuel in racing cars and in fuel cells, can be made by the reaction of carbon

monoxide and hydrogen.

CO(g) + 2H2(g) CH3OH(l)

Suppose 356 g of CO and 65.0 g of H2 are mixed and allowed to react. What is the limiting reactant in this case?

(b) Find the theoretical yield of methanol.

1. Write the mole ratios of the limiting reactant and the desired product.

LR: ________________

2. Calculate the number of moles of the product that will form from the given number of moles of the limiting reactant.

Product: ________________

4. Aluminium chloride can be made by the reaction of aluminium and chlorine, according to the following equation: 2Al(s) + 3Cl2(g) 2AlCl3(s). What is the limiting reactant if 157 g of Al is and 268 g of Cl2 is reacted?

(b) Find the theoretical yield of AlCl3. 1. Write the mole ratios of the limiting reactant and the desired product.

LR: ________________

2. Calculate the number of moles of the product that will form from the given number of moles of the limiting reactant.

Product: ________________

5. One of the components of the fuel mixture on the Apollo spacecraft involved a reaction with hydrazine, N2H4, and dinitrogen tetraoxide. The reaction produced nitrogen gas and water. (a) Write the balanced chemical equation for this reaction.

(b) If you mixed 150 g of hydrazine and 250 g of N2O4, what is the limiting reactant?

(c) Find the theoretical yield of N2. 1. Write the mole ratios of the limiting reactant and the desired product.

LR: ________________

2. Calculate the number of moles of the product that will form from the given number of moles of the limiting reactant.

Product: ________________

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