A student places a 4.00g of BaF2 in enough water to make a 250 mL solution. With stirring the concentration of

Question

the flouride ion rises to 0.0150g and then stops working. Use this data to determine the Ksp for BaF2

Answer 1

BaF2 = Ba+2 + 2F-1

Ksp = [Ba+2](F-1]^2

To calculate Ksp you need [Ba+2] and [F-1].  If you know the [F-1], the [Ba+2] is half as much (see the balanced equation)

You "know" the [F-1] if you change the grams of F to moles and then divide by LITERS of solution (not mL). Get this answer and then divide by 2 to get the Ba+2 and substitute into the Ksp.  Don't forget to square the [F-1]