The ph of a 0.10M HCN solution is 5.2?

Question

What is [CN^-^]? What is [HCN]? Where do H+ and CN^-^ ions come from?

Answer 1

HCN is called Hydrogen cyanide. ( [CN] is cyanide).

Hydrogen cyanide is a chemical compound with chemical formula HCN. A solution of hydrogen cyanide in water is called hydrocyanic acid. Hydrogen cyanide is a colorless, very poisonous, and highly volatile liquid that boils slightly above room temperature at 26 °C (78.8 °F). HCN has a faint, bitter, almond-like odor that some people are unable to detect due to a genetic trait.[1] Hydrogen cyanide is weakly acidic and partly ionizes in solution to give the cyanide anion, CN–. The salts of hydrogen cyanide are known as cyanides. HCN is a highly valuable precursor to many chemical compounds ranging from polymers to pharmaceuticals.

Answer 2

[H+]=[CN-] because a few molecules of HCN will transfer their protons to water forming hydronium ions (H3O+). In pH problems, hydronium ions are just considered to be protons, H+.

Calculate the [H3O+] from the pH

[H3O+] = 10^(-5.2). That will also be the concentration of CN- ions. The actual concentration of HCN will be 0.10 - [H+], but it'll pretty much be 0.10.