Question

According to the following chemical equilibrium:

OH + HCN <--> CN + H2O

What species impose the pH if the hydrocynaic acid (HCN) is used up? What is the pH of the solution?

Answer 1

After cosumption of all HCN, its a hydrlysis of CN- ion which impose pH. The reverse rection of above reaction is the hydrolysis of CN-.

CN + H₂O <---> HO- + HCN.

Also when there is excess HO- which left after complete consumption of HCN, its an excess HO- which impose pH.

pH of the solution is given as, pH = -log[H⁺]

For basic solutions i.e. solution with excess HO- ions first pOH is calculated and then pH + pOH = 14 formula is used.

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