Objective question (single correct answer).
i. `H_(3) PO_(4)` is a tribasic acid and one of its salt is `NaH_(2) PO_(4)`. What volume of `1M NaOH` solution should be added to `12 g` of `NaH_(2) PO_(4)` to convert in into `Na_(3) PO_(4)` ?
ii. The normality of a mixture obtained mixing `100 mL` of `0.2 m H_(2) SO_(4)` with `100 mL` of `0.2 M NaOH` is:
a. `0.05 N` b. `0.1 N` c. `0.15 N` d. `0.2 N`
iii. `100 mL` solution of `0.1 N HCl` was titrated with `0.2 N` `NaOH` solutions. The titration was discontinued after adding `30 mL` of `NaOH` solution. The reamining titration was completed by adding `0.25 N KOH` solution. The volume of `KOH` required from completing the titration is:
a. `70 mL` b. `35 mL` c. `32 mL` d. `16 mL`

Options

A. 0.0267
B. `0.2670`
C. `1.0267`
D. `1.1670`

Answer

B

Explanation

Normality of a mixture (N) = `(N_(1)V_(1)+N_(2)V_(2))/(V_(1)+V_(2))`
Normality `(N_(1))` of `H_(2)SO_(4)`=molarity`xx`basicity =`0.2xx2x=0.4`N
`N_(2)=0.2xx1=0.2N`
`V_(1)=100 mL , V_(2)=200 mL`
`N=(N_(1)V_(1)+N_(2)V_(2))/(V_(1)+V_(2))=(40+40)/(300)=(80)/(300)=0.2670 N`
Normality of mixture of acid and base (N')
`(N')=(N_(1)V_(1)~N_(2)V_(2))/(V_(1)V_(2))`