Question

15. (6 pts.) You have 0.669 g of an unknown acid, HA which reacts with NaOH according to the balanced chemical equation HA(aq) + NaOH(aq) - NaA(n) + H2O() If 36,04 ml. of 0.509 M NaOH is required to titrate the acid to the equivalence point, what is the molar mass of the acid?(4 pts.) Identify the acid (2 pts.)

Answer 1

mole of NaOH used = ( molarity of NaOH ) x ( Volume of NaOH used in liter )

= ( 0.509 ) x ( 36.04 /1000 )

=  0.01834 mole

From chemical reaction :-

mole of acid used = mole of NaOH used

than

mole of acid used = mole of NaOH used =  0.01834 mole

molar mass of acid is = gram of acid used / mole of acid used = 0.669 / 0.01834 = 36.477 g / mole = 36.5 g /mole

This molar mass match with molar mass of Hydrochloric acid ( HCl ) i.e. = 36.46 g/mol

Hence unknown Acid is Hydrochloric acid ,   HCl