How many mole of HCN will be required to prepare one litre buffer solution of pH =10.4 using 0.01 mol NaCN ? (Given .Ka ( HCN )=4 × 10-10)

Question

How many mole of HCN will be required to prepare one litre buffer solution of pH =10.4 using 0.01 mol NaCN ? (Given .Ka ( HCN )=4 × 10-10) (A) 2 × 10-2 mol (B) 1 × 10-3 mol (C) 4 × 10-4 mol (D) 9 × 10-3 mol

Tardigrade Admin · Accepted Answer

pH = pk a + log (( Salt / Acid )) 10.4=9.4+ log ((0.01/ x )) 1= log (0.01/ x ) ; 10=(0.01/ x ) x =0.001=10-3

Q. How many mole of $H CN$ will be required to prepare one litre buffer solution of $p H = 10.4$ using $0.01$ mol $N a CN$ ? (Given $K a (H CN) = 4 \times 1 0^{- 10})$

$2 \times 1 0^{- 2} m o l$

$1 \times 1 0^{- 3} m o l$

$4 \times 1 0^{- 4} m o l$

$9 \times 1 0^{- 3} m o l$

$p H = p k_{a} + lo g (\frac{S a lt}{A c i d})$
$10.4 = 9.4 + lo g (\frac{0.01}{x})$
$1 = lo g \frac{0.01}{x}; 10 = \frac{0.01}{x}$
$x = 0.001 = 1 0^{- 3}$

Q. How many mole of HCN will be required to prepare one litre buffer solution of pH=10.4 using 0.01 mol NaCN ? (Given Ka(HCN)=4×10−10)

2×10−2mol

1×10−3mol

4×10−4mol

9×10−3mol