Question about equilibium and how it shifts from left to right..10 points 4 best?

Question

My equation is Fe+3 + SCN-1 = Fe(SCN)3solid

and it asks what direction do you think the addition of Fe+3 will drive the equilibrium

so my question is: how do I tell which direction it will go? left or right?

(were using the Le Chartelier's principle: any change to a chemical reaction at equilibrium causes the reaction to move in the direction that will minimize the effect of the change.)

Answer 1

It will go to the right...since you've just increased the concentrations of Fe(3+), you've basically added stuff to the "left side of the scale"..to keep the "scale" balanced and in equilibrium the right side needs more stuff.

Answer 2

With Le Chatelier's principle the key is to define the stress. The most common stresses are to either add some ions (Fe+3) or remove some ions. The system, like us, will shift to remove the stress.

So in the case of the Fe+3, the system will shift to remove the extra Fe+3. How does it remove the Fe+3? Make it solid Fe(SCN)3. So the reaction will shift right.

If we were to remove some Fe+3, then the reaction will shift left. Why? Because the stress is not enough Fe+3. So the way that we relieve that stress is to form more Fe+3.

Hope that helps.