Answer:
C. hydrocyanic acid
Explanation:
The mixture of a weak acid (As hydrocyanic acid, HCN), with its conjugate base (Na⁺CN⁻) produce a buffer effect in the solution due the equilibrium:
HCN ⇄ CN⁻ + H⁺
Now, when NaOH (A base) is added to the mixture, the reaction with HCN is:
NaOH + HCN → Na⁺CN⁻ + H₂O
As the OH⁻ of NaOH are not affecting directly the H⁺ concentration, the pH does not increase dratically.
Right answer is:
C. hydrocyanic acid
A buffer contains 0.23 mol of hydrocyanic acid and 0.24 mol of sodium cyanide in 1.00 L of solution. Upon the addition of 0.05 mol of NaOH, the pH does not increase drastically because the NaOH reacts with the C. hydrocyanic acid present in the buffer solution.
A solution is prepared by dissolving 0.23 mol of hydrocyanic acid (HCN) and 0.24 mol of sodium cyanide (NaCN) in water sufficient to yield 1.00 L of solution.
Hydrocyanic acid is a weak acid since its Ka (4.9 . 10⁻¹⁰) << 1. The cyanide ion (CN⁻) coming from NaCN is its conjugate base. Together, they form a buffer system.
When a base is added, such as 0.05 moles of NaOH it reacts with the acid component and is neutralized by it.
NaOH + HCN ⇒ NaCN + H₂O
As a consequence of this neutralization, the pH does not increase drastically.
A buffer contains 0.23 mol of hydrocyanic acid and 0.24 mol of sodium cyanide in 1.00 L of solution. Upon the addition of 0.05 mol of NaOH, the pH does not increase drastically because the NaOH reacts with the C. hydrocyanic acid present in the buffer solution.
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