Question

What is the concentration of H3O+ ions in saliva if [OH-] = 4.22 x 10-10 M? Provide the pH and the classification of this sample of saliva.

Answer 1

pH=4.625

The classification of this sample of saliva : acid

Further explanation

The water equilibrium constant (Kw) is the product of concentration

the ions:

Kw = [H₃O⁺] [OH⁻]

Kw value at 25° C = 10⁻¹⁴

It is known [OH-] = 4.22 x 10⁻¹⁰ M

then the concentration of H₃O⁺:

`\tt 10^(-14)=4.22* 10^(-10)* [H_3O^+]\\\\(H_3O^+]=(10^(-14))/(4.22* 10^(-10))=2.37* 10^(-5)`

pH=-log[H₃O⁺]
`\tt pH=5-log~2.37=4.625`

Saliva⇒acid(pH<7)