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Decrease in volume

Posted: Sat Nov 14, 2015 9:51 pm
by 904611851
For the equation:
2HCl(g) + I(s) --> 2HI(g) + Cl2(g)

why does the number of moles of HCl increase when the volume in the container decreases?

Re: Decrease in volume

Posted: Sat Nov 14, 2015 10:55 pm
by Ronald Yang 2F
If the volume of the container decreases, essentially pressure in the container increases (pressure and volume have an inverse relationship). This pressure is created by the collisions of gas molecules. Thus, we only look at molecules in the gas phase. For 2HCl(g) + I(s) --> 2HI(g) + Cl2(g), we only look at the HCl, HI, and Cl2, so, to balance out the increase in pressure, the reaction shifts to the side with less moles, which is the left side. Thus, the number of moles of HCl would increase.