Does an increase in pressure always causes increase in molar concentration of each gaseous substance involved?

**Question**


***Statement*** :
"An increase in pressure (caused by decrease im volume) at equilibrium results in increase in molar concentration of each gaseous susbstance involved"


This statement is given true, so i tried this reasoning:


Since decrease in volume(V) causes increase in pressure and hence increase in no. of moles(n), so n/V increase hence molarity increases.


Is this reasoning correct? Please give the real reason for the statement.




Your reasoning is correct as long as there is a decrease in volume. Note that pressure can also increase with temperature and the volume can stay constant. In this case, the molarity will not change. Molarity is not a very useful unit for expressing gas concentrations in equilibria because you have to quote pressure, volume, temperature and of course moles to quote molarity. 


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I think the no of moles will remain constant the pressure and volume of a gas alternatively changes(they are inversely proportional when temp and mike's are constant).thus due to the decrease in volume and the no of moles remaining constant increases.
Apply the equation P=1/3(c(vrms)^2) now v RMS and m are constant in a particular temperature thus if pressure increases c also increases.


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