# Question ca9c5

May 24, 2016

Approx. $103 \cdot g$

#### Explanation:

$\text{Moles of copper}$ $=$ (82*g)/(63.55*g*mol^-1 $=$ $1.29 \cdot m o l$.

$\text{Moles of sulfur}$ $=$ (25*g)/(32.06*g*mol^-1 $=$ $0.78 \cdot m o l$.

Clearly the sulfur oxidant is in excess if the copper is incompletely oxidized; $0.66 \cdot m o l$ $C {u}_{2} S$ may be formed,

$0.66 \cdot m o l \times 159.16 \cdot g \cdot m o {l}^{-} 1$ $=$ ??g#

Look at your stoichiometric equation and divide by 2.

$2 C u + S \rightarrow C {u}_{2} S$

It tells you that approx. $63 \cdot g$ of copper metal react with approx. $16 \cdot g$ of sulfur. Why? Because that is the molar mass of each element is $63.55 \cdot g$ and $32.06 \cdot g$ respectively. Good luck in your test.