Question

A `7 L` container holds `7` mol and `18` mol of gasses A and B, respectively. Every three of molecules of gas B bind to one molecule of gas A and the reaction changes the temperature from `320^oK` to `330 ^oK`. By how much does the pressure change?

Answer 1

Pressure changes directly with amount of matter and with temperature. We'll do this in two steps.

Explanation:

If the reaction is of the form `A+3B->C` where `C=AB_3`:

(1)
In the reaction 18 mol of B will bind to 6 mol of A to form 6 mol of C (assuming C is also a gas!).
1 mol of A will be left. So now we have 7 mol in stead of 25 mol.
`p_1=p_0 xx7/25`

(2)
Temperature goes from 320 K to 330 K:
`p_(end)=p_1 xx330/320`

Total change:
`p_(end)=p_0xx7/25xx330/320~~0.29xxp_0`

Note:
More likely the reaction is of the form:
`A_2+3B_2->2C` where `C=AB_3`

In this case the number of moles goes from:
`7A+18B to 1A+12C`
And the fraction in step (1) will be `13/25`