Chemistry Math Question?

Question

When 40 mL of 0.266 M sulfuric acid is titrated with a standard solution of 0.278 M NaOH solution, what volume of base is required to reach the second equivalence point of the titration?

Answer 1

H2SO4 + NaOH ==> H2O + NaHSO4

NaHSO4 + NaOH ==> H2O + Na2SO4

To reach the second equivalence point, all of the H2SO4 must be neutralized, i.e. both protons.

The overall reaction is H2SO4 + 2NaOH ==> 2H2O + Na2SO4

Moles of H2SO4 present:

0.040 L x 0.266 moles/L = 0.01064 moles H2SO4

Moles NaOH needed:

0.01064 moles H2SO4 x 2 moles NaOH / mole H2SO4 = 0.02128 moles NaOH needed

Volume of NaOH needed:

(x L)(0.278 mole/L) = 0.02128 moles

x = 0.0765 L = 76.5 mls = 77 mls (to 2 significant figures)