20 mL of calcium hydroxide was consumed when it was reacted with 10 mL of unknown solution of H 2 SO 4 . Also 20 mL standard solution of 0 . 5 M HCl containing 2 drops of phenolphthalein was titrated with calcium hydroxide, the mixture showed pink colour when burette displayed the value of 35 . 5 mL whereas the burette showed 25 . 5 mL initially. The concentration of H 2 SO 4 is _______M . (Nearest integer)

Step-by-step solution

Titration principle is N 1 V 1 = N 2 V 2 N = Normality V = Volume of solution M 1 V 1 n 1 = M 2 V 2 n 2 M = molarity n = Valence factor of acid or base As pink colour is obtained on consumption of 10   ml of Ca ( OH ) 2 , we have 20 × 0 . 5 × 1 = 10 × M × 2 Molarity of Ca ( OH ) 2 = 10 20 = 1 2 M Also, moles of Ca ( OH ) 2 = mm of H 2 SO 4 1 2 × 20 = 10 × M Molarity of H 2 SO 4 = 1 M