Question

20 ml of the solution containg `Na_(2)CO_(3)` and `NaHCO_(3)` is titrated with `0.1MHCI` using Phenolphthalein indicator the end point was `10ml. 20ml` of the same solution is titrated with `0.1M HCI`, the end point was 25ml with Methylorange indicaor from the begining.
`NaHCO_(3)+HCl rarr NaCl +H_(2)O +CO_(2)`
`Na_(2)CO_(3)+2HCl rarr 2NaCl +CO_(2) +H_(2)O`
What is amount of `NaHCO_(3)` present in 1 litre of solution
A. `2.1g`
B. `1.05g`
C. `8.1g`
D. `0.844g`

Answer 1

Correct Answer - A
Using methyl orange,
`x +y = 25 xx 0.1 = 2.5, y = 2.5 - 2 = 0.5`
Wt of `NaHCO_(3)` in 20ml `=(0.5)/(1000) xx 84 = 0.042g`
wt of `NaHCO_(3)` in 1 lit `=(0.042)/(20) xx 1000 = 2.1g`