# Question 7be8c

Sep 2, 2017

The pressure would be 1029 Torr.

#### Explanation:

Henry’s law says that the concentration $c$ of a gas in a solvent is directly proportional to the partial pressure $p$ of the gas above the solvent.

The mathematical expression for Henry’s law is

$\textcolor{b l u e}{\overline{\underline{| \textcolor{w h i t e}{\frac{a}{a}} c = {k}_{\textrm{H}} p \textcolor{w h i t e}{\frac{a}{a}} |}}} \text{ }$

where ${k}_{\textrm{H}}$ is is a proportionality constant called the Henry's Law constant.

If we have the same solute in the same solvent at two different pressures ${p}_{1}$ and ${p}_{2}$, we can write

${c}_{1} = {k}_{\textrm{H}} {p}_{1}$

and

${c}_{2} = {k}_{\textrm{H}} {p}_{2}$

Dividing the two equations, we get

${c}_{1} / {c}_{2} = \frac{\textcolor{red}{\cancel{\textcolor{b l a c k}{{k}_{\textrm{H}}}}} {p}_{1}}{\textcolor{red}{\cancel{\textcolor{b l a c k}{{k}_{\textrm{H}}}}} {p}_{2}} = {p}_{1} / {p}_{2}$

p_2 = p_1 × c_2/c_1#

The volumes of solvent are the same, so we can use the masses of the solute instead of concentrations.

${p}_{2} = \text{772.0 Torr" × (0.4960 color(red)(cancel(color(black)("g"))))/(0.3720 color(red)(cancel(color(black)("g")))) = "1029 Torr}$