# How to find the initial pressure?

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Here's my work :

#T_1=74+273.15 = 347.15 k #

#T_2 = 120+273.15 = 393.15 k #

#P_2=1.79 atm #

#P_1 T_1 = P_2 T_2#

#P_1 = ( 393.15*1.79)/347.15 = 2.027 atm#

Could somebody solve this problem ?

Here's my work :

Could somebody solve this problem ?

##### 1 Answer

#### Answer:

The initial pressure was 1.58 atm.

#### Explanation:

Since the volume is constant but the pressure and temperature are changing, this is an example of **Gay-Lussac's Law**:

#color(blue)(bar(ul(|color(white)(a/a)p_1/T_1=p_2/T_2color(white)(a/a)|)))" "#

We can rearrange the above formula to get

#p_1=p_2 × T_1/T_2#

Your data are:

The initial pressure was 1.58 atm.

(You used the wrong formula for Gay-Lussac's Law.)