Question 3.15: Calculating Quantities of Reactants and Products: Amount (mo......
Calculating Quantities of Reactants and Products: Amount (mol) to Mass (g)
Problem During the roasting process, how many grams of sulfur dioxide form when 10.0 mol of copper(I) sulfide reacts?
Plan We use the balanced equation in Sample Problem 3.14, but here we are given amount of reactant (10.0 mol of Cu_2S) and need the mass (g) of product (SO_2) that forms. We find the amount (mol) of SO_2 using the molar ratio (2 mol SO_2/2 mol Cu_2S) and then multiply by its molar mass (64.07 g/mol) to find the mass (g) of SO_2 (see the road map (Fig 3.15)).
Solution Combining the two conversion steps into one calculation, we have
\text{Mass (g) of }SO_2 = 10.0 \cancel{\text{mol } Cu_2S} × \frac{2 \cancel{\text{mol }SO_2}}{2 \cancel{\text{mol }Cu_2S}} × \frac{64.07 g SO_2}{1 \cancel{\text{mol }SO_2}} = 641 g SO_2Check The answer makes sense, since the molar ratio shows that 10.0 mol of SO_2 is formed and each mole weighs about 64 g. We rounded to three significant figures.
