1.

200 " mL of " a solution of a mixture of NaOH and `Na_2CO_3` was first titrated with 0.1 M HCl using phenolphthalein indicator. 17.5 " mL of " HCl was required for the same HCl was again required for next end point. Find the amount of NaOH and `Na_2CO_3` in the mixture.

Answer» With phenolphthalein
`m" Eq of "Hcl` used for 200 mL solution`=17.5xx0.1xx1`
`=1.75`
Let a and b m" Eq of "NaOH and `Na_(2)CO_(3)` respectively.
`a+(b)/(2)=1.75` .(i)
With methyl orange indicator
m" Eq of "HCl used for solution after first end point
`=2.5xx0.1xx1=0.25`
`(b)/(2)=0.25` .(ii)
By equations (i) and (ii)
`a(mEq. of NaOH)=1.5`
Weight of NaOH`=1.5xx10^(-3)xx40`
`=(0.06g)/(200mL)`
`b(m" Eq of "Na_(2)CO_(3))=0.5`
Weight of `Na_(2)CO_(3)=0.5xx10^(-3)xx(106)/(2)`
`=(0.0265)/(200mL)`


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