3 ( mathrm{g} ) of activated charcoal was added to ( 50 mathrm{mL} ) of acetic acid solution ( (0.06 mathrm{N}) ) in a flask. After an hour it was filtered and the strength of the filtrate was found to be ( 0.042 mathrm{N} ). The amount of acetic acid adsorbed (per gram of charcoal) is
(a) ( 18 mathrm{mg} )
(b) ( 36 mathrm{mg} )
(c) ( 42 mathrm{mg} )
(d) ( 54 mathrm{mg} )

Given, initial strength of acetic acid ( =0.06 mathrm{N} ) Final strength ( =0.042 mathrm{N} ; quad ) Volume ( =50 mathrm{mL} )
( therefore ) Initial millimoles of ( mathrm{CH}_{3} mathrm{COOH}=0.06 times 50=3 )
Final millimoles of ( mathrm{CH}_{3} mathrm{COOH}=0.042 times 50=2.1 )
( therefore ) Millimoles of ( mathrm{CH}_{3} mathrm{COOH} ) adsorbed ( =3-2.1=0.9 mathrm{mmol} )
( left(m_{mathrm{O}_{2}}right) quad=0.9 times 60 mathrm{mg}=54 mathrm{m} )