# A level chem Kp question

The answer is b , which I got by doing process of elimination but I dont get why it’s correct, surely if the partial pressure of Nitrogen decreases so will the Kp since you need it to sub into the Kp formula
(edited 9 months ago)
Original post by 1234kelly
The answer is b , which I got by doing process of elimination but I dont get why it’s correct, surely if the partial pressure of Nitrogen decreases so will the Kp since you need it to sub into the Kp formula

The only thing that affects equilibrium constant is temperature.

If you change the pressure in the system (when there is an unequal number of moles on each side) the quotient ceases to be equal to kp and the system must respond to restore the value of kp

Try it out on a simple example:

X2(g) <==> 2X(g)

If the pp of X2 and X are equal to 2Pa at equilibrium then kp = (2)2/2 = 2

Reduce the pressure of X to 1 and the quotient then equals 4. This is not equal to kp so the system responds by making more X(g), until the equality: quotient = kp is satisfied.

Here is another example:

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Colourful Solutions IB Chemistry Testing and Notes
Original post by charco
The only thing that affects equilibrium constant is temperature.

If you change the pressure in the system (when there is an unequal number of moles on each side) the quotient ceases to be equal to kp and the system must respond to restore the value of kp

Try it out on a simple example:

X2(g) <==> 2X(g)

If the pp of X2 and X are equal to 2Pa at equilibrium then kp = (2)2/2 = 2

Reduce the pressure of X to 1 and the quotient then equals 4. This is not equal to kp so the system responds by making more X(g), until the equality: quotient = kp is satisfied.

Here is another example:

-----------------------------------------------------------------------------------------------
Signature
Colourful Solutions IB Chemistry Testing and Notes

Thank you so so much ,its made things a lot clearer!