Answer:
0.34mol NaCN
0.082mol Ba(OH)₂
Explanation:
Options:
0.34mol NaCN
0.33mol NaClO₄
0.34mol HClO₄
0.16mol HClO₄
0.082mol Ba(OH)₂
A buffer is defined as the aqueous mixture of a weak acid with its conjugate base or vice versa.
Hydrocyanic acid, HCN is a weak acid. Its equilibrium in water is:
HCN + H₂O → CN⁻ + H₃O⁺
Where the CN⁻ ion is the conjugate base.
Thus, to convert the HCN solution in a buffer you must add CN⁻ ions to the solution.
In solution, 0.34mol NaCN converts 0.34 mol CN⁻, thus, you can convert this solution in a buffer with this addition.
The addition of HClO₄ or NaClO₄ don't produce a buffer because you would not have CN⁻ ions in solution.
Now, HCN reacts with Ba(OH)₂ thus:
2HCN + Ba(OH)₂ → 2H₂O + Ba²⁺ + 2CN⁻
Thus, the addition of 0.082mol Ba(OH)₂ could convert this solution in a buffer because CN⁻ is produced in its reaction with HCN
