100 mL of 0.5 M aqueous solution is mixed with 80 mL of 1.25 M HCl solution. The pH of the final solution is (Given: of are and respectively)

Question

100 mL of 0.5 M ${Na}_{3} {PO}_{4}$ aqueous solution is mixed with 80 mL of 1.25 M HCl solution. The pH of the final solution is (Given: $K_{a_{1}}, K_{a_{2}}, K_{a_{3}}$ of $H_{3} {PO}_{4}$ are $10^{- 3}, 10^{- 5}$ and $10^{- 7}$ respectively)

Smart Achievers · Accepted Answer

(2)

Hint: m. moles of ${Na}_{3} {PO}_{4} = 50$

M moles of HCl = 100

Final solution will have ${NaH}_{2} {PO}_{4}$ (amphoteric salt)

$∴$ $pH = \frac{p K_{a 1} + p K_{a 2}}{2} = 4$

Solution

Q.
100 mL of 0.5 M ${Na}_{3} {PO}_{4}$ aqueous solution is mixed with 80 mL of 1.25 M HCl solution. The pH of the final solution is (Given: $K_{a_{1}}, K_{a_{2}}, K_{a_{3}}$ of $H_{3} {PO}_{4}$ are $10^{- 3}, 10^{- 5}$ and $10^{- 7}$ respectively)

1 6

2 4

3 3.5

4 4.7

Ans.
(2)

Hint: m. moles of ${Na}_{3} {PO}_{4} = 50$

M moles of HCl = 100

Final solution will have ${NaH}_{2} {PO}_{4}$ (amphoteric salt)

$∴$ $pH = \frac{p K_{a 1} + p K_{a 2}}{2} = 4$

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