Question

Suppose you have a 10.00mL solution of H₂A, a diprotic weak acid, which has a pk_a1 of 4.00 and a pk_a2 of 9.00. The formal concentration is 0.100M and it is titrated by 0.100M NaOH.

(a) Write the two major reactions during the titration. Find the two equivalence points.

(b) For each of the following delivered volumes (mL) of the titrant, find the pH: Vb=0, 2.00, 5.00, 9.90, 10.00, 12.00, 15.00, 20,00 and 21.00mL.

Show all work please! Thanks

Answer 1

(a) H​​​​​​2​​​​A(aq) + NaOH(aq) NaHA(aq) + H​​​​​​2​​​​​O(l)

NaHA(aq) + NaOH(aq) Na​​​​​2​​​​A(aq) + H​​​​​​2O(l)

M1V1 = M2V2

10.00ml ×0.100M = V2 × 0.100M

V2 = 10.0ml

First equivalent point = 10.0ml

Second equivalent point = 20.0ml

(b)