The exact volumes of 1 M NaOH solution required to neutralize 50 mL of 1 M H₃PO₃ solution and 100 mL of 2 M H₃PO₂ solution, respectively, are:

a. 100 mL and 50 mL

b. 50 mL and 50 mL

c. 100 mL and 100 mL

d. 100 mL and 200 mL

Answer: (d)

(1) 2NaOH + H₃PO₃ → Na₂HPO₃ + 2H₂O

100 mmole 50mmole

100 mmole = M × V_ml

100 mmole = 1 × V_ml

V_ml = 100 ml

(2) NaOH + H₃PO₂ → NaH₂PO₂ + H₂O

200 mmole 200mmole

200 mmole = M × V_ml

200 mmole=1 × V_ml

V_ml = 200 ml