Stoichiometry worksheet with mole-to-mass conversion problems and chemical equations.

Here are the step-by-step solutions for the stoichiometry problems.

Problem 1

Reaction: $\text{Mg}(s) + 2\text{HCl}(aq) \rightarrow \text{MgCl}_2(aq) + \text{H}_2(g)$

a. How many grams of HCl are consumed by the reaction of 2.50 moles of magnesium?

1. Find the mole ratio: Look at the balanced equation. For every 1 mole of Mg, you need 2 moles of HCl.
2. Calculate moles of HCl:
$$2.50 \text{ mol Mg} \times \frac{2 \text{ mol HCl}}{1 \text{ mol Mg}} = 5.00 \text{ mol HCl}$$
3. Find molar mass of HCl:
* H = $1.01$ g/mol
* Cl = $35.45$ g/mol
* Total = $36.46$ g/mol
4. Convert to grams:
$$5.00 \text{ mol} \times 36.46 \text{ g/mol} = 182.3 \text{ g}$$

b. What is the mass in grams of H₂ gas when 4.0 moles of HCl is added to the reaction?

1. Find the mole ratio: The equation shows that 2 moles of HCl produce 1 mole of H₂.
2. Calculate moles of H₂:
$$4.0 \text{ mol HCl} \times \frac{1 \text{ mol H}_2}{2 \text{ mol HCl}} = 2.0 \text{ mol H}_2$$
3. Find molar mass of H₂:
* H = $1.01$ g/mol
* H₂ = $2 \times 1.01 = 2.02$ g/mol
4. Convert to grams:
$$2.0 \text{ mol} \times 2.02 \text{ g/mol} = 4.04 \text{ g}$$

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Problem 2

Reaction: $\text{CaC}_2(s) + 2\text{H}_2\text{O}(l) \rightarrow \text{C}_2\text{H}_2(g) + \text{Ca(OH)}_2(aq)$

a. If 3.20 moles of CaC₂ are consumed, how many grams of H₂O are needed?

1. Find the mole ratio: You need 2 moles of H₂O for every 1 mole of CaC₂.
2. Calculate moles of H₂O:
$$3.20 \text{ mol CaC}_2 \times \frac{2 \text{ mol H}_2\text{O}}{1 \text{ mol CaC}_2} = 6.40 \text{ mol H}_2\text{O}$$
3. Find molar mass of H₂O:
* H ($2 \times 1.01$) + O ($16.00$) = $18.02$ g/mol
4. Convert to grams:
$$6.40 \text{ mol} \times 18.02 \text{ g/mol} = 115.33 \text{ g}$$

b. How many grams of Ca(OH)₂ would be formed with 3.20 moles of CaC₂?

1. Find the mole ratio: The ratio of CaC₂ to Ca(OH)₂ is 1:1.
2. Calculate moles of Ca(OH)₂:
$$3.20 \text{ mol CaC}_2 \times \frac{1 \text{ mol Ca(OH)}_2}{1 \text{ mol CaC}_2} = 3.20 \text{ mol Ca(OH)}_2$$
3. Find molar mass of Ca(OH)₂:
* Ca ($40.08$) + 2 $\times$ [O ($16.00$) + H ($1.01$)]
* $40.08 + 2(17.01) = 74.10$ g/mol
4. Convert to grams:
$$3.20 \text{ mol} \times 74.10 \text{ g/mol} = 237.12 \text{ g}$$

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Problem 3

Reaction: $2\text{C}_2\text{H}_2(g) + 5\text{O}_2(g) \rightarrow 4\text{CO}_2(g) + 2\text{H}_2\text{O}(g)$

How many moles of water (H₂O) are produced when 25.0 grams of C₂H₂ burns completely?

1. Find molar mass of C₂H₂:
* C ($2 \times 12.01$) + H ($2 \times 1.01$) = $24.02 + 2.02 = 26.04$ g/mol
2. Convert grams of C₂H₂ to moles:
$$25.0 \text{ g} / 26.04 \text{ g/mol} = 0.960 \text{ mol C}_2\text{H}_2$$
3. Find the mole ratio: The equation produces 2 moles of H₂O for every 2 moles of C₂H₂ (a 1:1 ratio).
4. Calculate moles of H₂O:
$$0.960 \text{ mol C}_2\text{H}_2 \times \frac{2 \text{ mol H}_2\text{O}}{2 \text{ mol C}_2\text{H}_2} = 0.960 \text{ mol H}_2\text{O}$$

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Problem 4

Reaction: $3\text{Mg} + 1\text{Fe}_2\text{O}_3 \rightarrow 2\text{Fe} + 3\text{MgO}$

How many moles of iron, Fe, are produced with 25.0 grams of magnesium, Mg?

1. Find molar mass of Mg: $24.31$ g/mol
2. Convert grams of Mg to moles:
$$25.0 \text{ g} / 24.31 \text{ g/mol} = 1.028 \text{ mol Mg}$$
3. Find the mole ratio: For every 3 moles of Mg, you get 2 moles of Fe.
4. Calculate moles of Fe:
$$1.028 \text{ mol Mg} \times \frac{2 \text{ mol Fe}}{3 \text{ mol Mg}} = 0.685 \text{ mol Fe}$$

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Problem 5

Reaction: $\text{NH}_4\text{NO}_3(s) \rightarrow \text{N}_2\text{O}(g) + 2\text{H}_2\text{O}(l)$

a. How many moles of NH₄NO₃ are required to produce 33.0g of N₂O?

1. Find molar mass of N₂O:
* N ($2 \times 14.01$) + O ($16.00$) = $28.02 + 16.00 = 44.02$ g/mol
2. Convert grams of N₂O to moles:
$$33.0 \text{ g} / 44.02 \text{ g/mol} = 0.750 \text{ mol N}_2\text{O}$$
3. Find the mole ratio: The ratio of NH₄NO₃ to N₂O is 1:1.
4. Calculate moles of NH₄NO₃:
$$0.750 \text{ mol N}_2\text{O} \times \frac{1 \text{ mol NH}_4\text{NO}_3}{1 \text{ mol N}_2\text{O}} = 0.750 \text{ mol NH}_4\text{NO}_3$$

b. How many moles of water are produced with 45.0g of N₂O?

1. Convert grams of N₂O to moles:
$$45.0 \text{ g} / 44.02 \text{ g/mol} = 1.022 \text{ mol N}_2\text{O}$$
2. Find the mole ratio: For every 1 mole of N₂O, 2 moles of H₂O are produced.
3. Calculate moles of H₂O:
$$1.022 \text{ mol N}_2\text{O} \times \frac{2 \text{ mol H}_2\text{O}}{1 \text{ mol N}_2\text{O}} = 2.04 \text{ mol H}_2\text{O}$$

Final Answer:
1a. 182 g HCl
1b. 4.0 g H₂
2a. 115 g H₂O
2b. 237 g Ca(OH)₂
3. 0.960 mol H₂O
4. 0.685 mol Fe
5a. 0.750 mol NH₄NO₃
5b. 2.04 mol H₂O