25 ml from a stock solution containing `NaHCO_(3)` and `Na_(2)CO_(3)` was diluted to 250 ml with `CO_(2)` free distilled water. 25 ml of the diluted solution when titrated with 0.12 M HCl required 8 ml., when phenolphthalein was used as an indicator.
`Na_(2)CO_(3) + HCl overset("HPh")(rarr)NaHCO_(3)`
When 20 ml of diluted solution was titrated with same acid it required 18 ml when methlyorange was used as an indicator.
`Na_(2)CO_(3)+2HCloverset("MeOH")(rarr)2NaCl+H_(2)O +CO_(2)`
`NaHCO_(3) +HCl overset( MeOH)(rarr) NaCl +H_(2)O +CO_(2)`
Millimoles of `NaHCO_(3)` present in stock solution.

Options

A. 0.624
B. 2.16
C. 1.536
D. 7.8

Answer

D