Question

25g of a sample of oleum is labled as 110%. The amount of H2O which should be added to this sample to get 50% H2SO4 (w/w%) is
(Assuming density of water =1g/ml)

Answer 1

Here is your answer.....
Molecular formula of Oleum is H2S2O7
​Molar Mass of H2S2O7 = 178 g/mol
​Molar mass of H2SO4 = 98 g /mol
Since the sample is 110 %, the amount of H2SO4 given by the sample is :
25g ​ x 110/100 = 27.5 g

Amount of water in given sample :
H2S2O7 + H2O →2H2SO4
178 g oleum + 18 g water → 196 g sulfuric acid
According to equation, 18 g of water was used to give 196 g H2SO4
So, amount of water used in above sample = 18g water/196 ​g H2SO4 x 27.5 g H2SO4
= 2.52 g water

To make 50% w/w solution of H2SO4, the amount of water added =
27.5 g - 2.52 g = 24.98 g water = 24.98 ml water

Answer 2

Answer:

30 gm

Explanation:

molar mass of h2so4=98

molar mass of h2o=18

molar mass of h2s2o7=178