60 grams of sodium hydroxide is required to completely neutralize 49 grams of sulphuric acid, percentage purity of sodium hydroxide sample is

2NaOH + H2SO4→Na2SO4+2H2O ; 2×40g      98g 80 grams of pure NaOH is required to neutralize 98 grams of H2SO4; 40 grams of pure NaOH is required to neutralize 49 grams of H2SO4; But in the given question, 60 grams of NaOH was required; Percentage purity of NaOH=4060×100=66.6%