Question

If the temperature of a gas rose from standard temperature to 35 degrees Celsius, what was the initial pressure applied to it if the final pressure is 72.5 psi?

If the temperature of a gas rose from standard temperature to 35 degrees Celsius, what was the initial pressure applied to it if the final pressure is 72.5 psi?

Answer 1

`"66 psi"`.

Explanation:

This is what we're given:

• `T_1` or initial temperature at `"0 °C"`. This is `273.15 K`.
• `T_2` or final temperature at `"25 °C"`. This is `298.15 K`.
• `P_2` or final pressure at `"72.5 psi"`.

We have to find `P_1`, or initial temperature.
The gas law that equates all of these variables is Gay-Lussac's Law:

`P_1/T_1 = P_2/T_2`

We can rearrange this to have `P_1` on one side! :)

`P_1 = T_1 xx P_2/T_2`

Then, we just need to plug in the variables:

`P_1 = T_1 xx P_2/T_2`
`P_1 = "273.15 K" xx ("72.5 psi")/"298.15 K"`

`P_1 = "273.15" cancel("K") xx ("72.5 psi")/("298.15" cancel("K"))`
`P_1 = "66 psi"`