JEE Main levelSingle correct optionDifficulty 2 of 3eq046
A 1.25g sample of impure NaOH (impurity is neutral to HCl) is dissolved in water and neutralised by 36.4mL of 0.500NHCl. The percentage purity of the sample (NaOH=40) is:
A29.1%
B58.2%
C91.0%
D72.8%
Answer: B
Equivalents of HCl=0.500×0.0364=0.0182, which equals the equivalents (moles) of NaOH. Mass of NaOH=0.0182×40=0.728g. Purity =0.728/1.25×100=58.2%.