A solution is prepared by dissolving 0.23 mol of hydrocyanic acid and 0.24 mol of sodium cyanide in water sufficient to yield 1.00 L of solution. The addition of 0.05 mol of NaOH to this buffer solution causes the pH to increase slightly. The pH does not increase drastically because the NaOH reacts with the present in the buffer solution. The Ka of hydrocyanic acid is 4.9 × 10^-10.

A. cyanide

B. H2O

C. hydrocyanic acid

D. H3O+

E. This is a buffer solution: the pH does not change upon addition of acid or base.

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

acid rain does not usually kill trees directly. instead, it is more likely to weaken the trees by damaging their leaves, limiting the nutrients available to them, or poisoning them with toxic substances slowly released from the soil. the main atmospheric pollutants that affect trees are nitrates and sulphates.

answer: -

reaction:

na + cl ⇌ nacl

balanced chemical equation:

na + 2cl ⇌ nacl2

sodium + clorine goes to form sodium chloride (table salt).

the product is nacl2.

and the reactants are na and cl.

(note: if you don’t know what ⇌ means, read below: -

⇌(double head arrow) means reversible reaction).