Question

1. how many grams of lithium nitrate, lino₃, will be needed to make 250 grams of lithium sulfate, li₂so₄? molar mass of lino₃ = 68.945 g/mol and molar mass of li₂so₄ = 109.944 g/mol

pb(so₄)₂ + 4 lino₃ → pb(no₃)₄ + 2 li₂so₄

1. if 6.5 moles of ag is produced, how many grams of cu are needed?

cu(s) + 2 agno₃(aq) → cu(no₃)₂(aq) + 2 ag(s)

Explanation:

Problem 5

Step1: Calculate moles of $\text{Li}_2\text{SO}_4$

Moles of $\text{Li}_2\text{SO}_4 = \frac{\text{Mass}}{\text{Molar Mass}} = \frac{250\ \text{g}}{109.944\ \text{g/mol}} \approx 2.274\ \text{mol}$

Step2: Mole ratio of $\text{LiNO}_3$ to $\text{Li}_2\text{SO}_4$

From reaction: $\frac{n(\text{LiNO}_3)}{n(\text{Li}_2\text{SO}_4)} = \frac{4}{2} = 2$
$n(\text{LiNO}_3) = 2 \times 2.274\ \text{mol} = 4.548\ \text{mol}$

Step3: Calculate mass of $\text{LiNO}_3$

Mass of $\text{LiNO}_3 = n \times \text{Molar Mass} = 4.548\ \text{mol} \times 68.945\ \text{g/mol} \approx 313.6\ \text{g}$

Step1: Mole ratio of $\text{Cu}$ to $\text{Ag}$

From reaction: $\frac{n(\text{Cu})}{n(\text{Ag})} = \frac{1}{2}$
$n(\text{Cu}) = \frac{1}{2} \times 6.5\ \text{mol} = 3.25\ \text{mol}$

Step2: Calculate mass of $\text{Cu}$

Molar mass of $\text{Cu} = 63.55\ \text{g/mol}$
Mass of $\text{Cu} = 3.25\ \text{mol} \times 63.55\ \text{g/mol} = 206.5375\ \text{g}$

Answer:

$\approx 314\ \text{grams}$ (rounded to 3 significant figures)

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Problem 6