Manipal Entrance Test 2013 Chemistry Paper

H2S2O7+H2O→2H2SO4
SO3 of H2S2O7 is converted into H2SO4, hence SO3 acts also as a dibasic acid.
Eq. wt. (SO3)=

M

2

=40
Let H2SO4 in fuming H2SO4=x g
SO3=(1−x)g
Equivalent of H2SO4=

x

49

SO3=

1−x

40

Equivalent of NaOH used =

26.7×0.8

1000

=0.02136

x

49

+

1−x

40

=0.02136
x=0.7927 g H2SO4 in 1g oleum.
Percentage of H2SO4=79.27%
SO3=20.73%