Question

In the reaction
HCl + NaOH --> NaCl + H2O + x cal
H2SO4 + 2NaOH --> Na2SO4 + 2H2O + y cal
(1) x = y
(2) x = 2y
(3) x = y/2
(4) x2 = y

Answer 1

HCl + NaOH  NaCl + H2O
So number of moles of water formed = 0.1
Number of moles of acid used = Number of moles of alkali
= C x V (in litres) = 1 x 0.1 = 0.1
Use proportion to find the amount of heat given out when 1 mole
of water is formed.
0.1 mole  -5.18 kJ
So 1 mole  1/0.1 x –5.18 = -51.8 kJ mol-1

Answer 2

The reaction of HCl with NaOH involves reaction of one mole of ions while reaction of H2SO4 with NaOH involves 2 moles. Enthalpy change for the second reaction is twice that of the first. So ans is the y= 2x i.e, y/2 =x.