# Question 41182

Jul 2, 2015

You'd need 87.5 g of chlorine gas.

#### Explanation:

The balanced chemical equation for this reaction looks like this

${P}_{4 \left(s\right)} + \textcolor{red}{6} C {l}_{2 \left(g\right)} \to \textcolor{b l u e}{4} P C {l}_{3 \left(l\right)}$

Chlorine and phosphorus trichloride have a $\textcolor{red}{3} : \textcolor{b l u e}{2}$ mole ratio, which means that the reaction will always need 3/2 times more moles of chlorine gas than the number of moles of phosphorus trichloride produced.

So, in order to produce 0.823 moles of phosphorus trichloride, the reaction needs

0.823cancel("moles"PCl_3) * (color(red)(3)" moles "Cl_2)/(color(blue)(2)cancel("moles"PCl_3)) = "1.2345 moles" $C {l}_{2}$

To get the mass in grams that would contain this many moles, use chlorine gas' molar mass

1.2345cancel("moles" Cl_2) * "70.906 g"/(1cancel("mole"Cl_2)) = "87.533 g"#

Rounded to three sig figs, the number of sig figs you gave for the number of moles of phosphorus trichloride produced, the answer will be

${m}_{C {l}_{2}} = \textcolor{g r e e n}{\text{87.5 g}}$