# For the reactions, H2(g)+Cl2(g)----->2HCl(g)+xKJ H2(g)+Cl2(g)----->2HCl(l)+yKJ Which one of the following statement is correct? A)x>y B)x<y C)x=y D)more data required

May 30, 2016

This is quite a difficult question in that we have to make assumptions: I think the answer is $B$

#### Explanation:

${H}_{2} \left(g\right) + C {l}_{2} \left(g\right) \rightarrow 2 H C l \left(g\right) + {\Delta}_{1}$

${H}_{2} \left(g\right) + C {l}_{2} \left(g\right) \rightarrow 2 H C l \left(l\right) + {\Delta}_{2}$

The difference between ${\Delta}_{1}$ and ${\Delta}_{2}$ is the process:

$2 H C l \left(l\right) + \Delta \rightarrow 2 H C l \left(g\right)$

Energy is used to boil the liquid. ${\Delta}_{2}$ as written should be larger than ${\Delta}_{1}$ (i.e. when the gas is condensed energy is released).

Note that the fact that exothermic reactions (and this one certainly is) are written as NEGATIVE, is a distractor. Here, because the energy is listed as a product (and not as a separate thermoodynamic property), we should be able to say that ${\Delta}_{2} > {\Delta}_{1}$. That is we get more energy out when the product is a liquid than when it is a gas.

Others may have a different take on this (and they certainly may have a better way of rationalizing the answer!).