Chemistry help please?

Question

consider a solution containing 0.100 M flouride ions and 0.126 M hydrogen flouride. The concentration of fluoride ions after the addition of 5.00 mL of 0.0100 M HCI to 25.0 mL of this solution is .......

Answer 1

The initial concentration of F- is 0.100 M + 0.126 M = 0.226 M. Nothing happens chemically when the HCl is added, so all we are doing by adding the HCl solution is diluting the F- solution with respect to [F-]. Therefore, we can then use the equation C1V1 = C2V2:

(0.226 M) (25.0 mL) = C2 (5.00 mL + 25.0 mL);

[F-] = C2 = 0.188 M.