1.25g of a sample of Na2CO3 and Na2SO4 is dissolved in 250ml solution. 25ml of this solution neutralises 20ml of 0.1NH2SO4. The % of Na2CO3 in this sample is:
A
84.8%
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B
8.48%
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C
15.2%
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D
42.4%
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Solution
The correct option is A84.8% The equivalent weight of Na2CO3 is 53.
Let the amount of Na2CO3 present in the mixture be xg. Na2SO4 will not react with H2CO3.
Then, the number of gram equivalents of Na2CO3= the number of gram equivalents of H2SO4.
x53=20×0.1×101000
∴x=1.06g
Note: We have divided with 1000 to convert the volume of H2SO4 from mL to L. We have multiplied with 10 as out of 250 mL of Na2SO4 solution, only 25 mL is used for neutralisation with H2SO425025=10
The number of gram equivalents of H2SO4 are obtained by multiplying volume with normality.