An acid-base equilibrium system is created by dissolving 0.10 mol HF in water to a volume of 1.0 L. What is the effect of adding 0.050mol F(aq) to this solution?

The equation for the equilibrium is



You know the concentration of HF. You haven't given me any Ka for HF so you can't solve this quantitatively.

Remember that



So, from that you can calculate the concentration of [F-] and figure out what happens to the equilibrium (it will drive it to the left).