Br2(l)+Cl2(g) (double arrow) 2BrCl(g)

Question

dH=+29.4 kJ/mol

I am having trouble understanding this. Will the system shift left, right, or unchanged and why?

a.Increasing Temp.
b. Increasing pressure in flask by adding Ar.
c. Increasing volume of flask
d. Adding Br2(l)...is answer move right
e. Removing Cl2(g)...is " left?
f. Adding BrCl(g)...is " left?
g. Adding catalyst

Answer 1

It's easy to understand if you look at it this way. Le Chateier's Principle tells us that when a stress is added to a system in equilibrium, the system will shift so as to undo what we've done to it.
The equation tells you that heat is given off when it reacts left to right. I might rewrite the equation as this to emphasize that.
Br2(l)+Cl2(g)<==>2BrCl(g) + HEAT

So if the system adds heat in reacting from left to right and we add more heat, the system will try to get rid of the excess heat we've added. So it will shift to the left meaning that if the reaction goes from right to left it USES up the heat. right?
b. In pressure problems of this kind it shift to the side with fewer mols (of gas). In this case it will not shift because both sides contain 2 moles.
c. For volume changes just convert to what that means with pressure. For example increasing volume means pressure is decreased and now revert to counting mols.
d is right
e is right
f is right
g. A catalyst NEVER shifts the equilibrium but it does change the rate of the reaction.