How would you do this question:

A student dissolved 5.0 g of vitamin C in
250 mL of water. The molar mass of ascorbic acid is 176 g/mol, and its Ka is 8.0 × 10−5. Calculate the pH of the solution. Note: Abbreviate the formula of ascorbic acid to HAsc.

1 answer

mols HAsc = 5/molar mass = approx 0.03 but you need to do it more accurately.

........HAsc ==> H^+ + Asc^-
I......0.03......0......0
C.......-x.......x.......x
E......0.03-x....x......x

Substitute the E line into Ka expression for HAsc and solve for x, then convert to pH.