# Question 4a2ed

May 12, 2017

The final temperature is -149 °C.

#### Explanation:

Since the volume is constant, this is an example of a problem involving Gay-Lussac's Pressure-Temperature Law:

$\textcolor{b l u e}{\overline{\underline{| \textcolor{w h i t e}{\frac{a}{a}} {p}_{1} / {T}_{1} = {p}_{2} / {T}_{2} \textcolor{w h i t e}{\frac{a}{a}} |}}} \text{ }$

We can rearrange this formula to get

T_2 = T_1 × p_2/p_1#

${p}_{1} = \text{450 mmHg"; T_1 = "15 °C" = "288.15 K}$
${p}_{2} = \text{225 mmHg"; T_2 = "?}$
${T}_{2} = \text{288.15 K" × (225 color(red)(cancel(color(black)("mmHg"))))/(450 color(red)(cancel(color(black)("mmHg")))) = "144.1 K" = "-129 °C}$