Question

Calculate the concentration of H3O⁺ in a solution that contains 6.25 × 10-9 M OH⁻ at 25°C. Identify the solution as acidic, basic, or neutral. A) 6.38 × 10-9 M, basic B) 1.60 × 10-6 M, acidic C) 7.94 × 10-11 M, acidic D) 7.38 × 10-3 M, basic E) 4.92× 10-5 M, acidic

Answer 1

Answer: B)
`1.60* 10^(-6)` M, acidic

Step-by-step explanation:

pH or pOH is the measure of acidity or alkalinity of a solution.

pH is calculated by taking negative logarithm of hydrogen ion concentration and pOH is calculated by taking negative logarithm of hydroxide ion concentration.

Acids have pH ranging from 1 to 6.9, bases have pH ranging from 7.1 to 14 and neutral solutions have pH equal to 7.

`pH=-\log [H_3O^+]`

`pOH=-log{OH^-}`

`pH+pOH=14`

Given :
`[OH^-]=6.25* 10^(-9)M`

`pOH=-log[6.25* 10^(-9)M]`

`pOH=8.20`

`pH=14-8.20=5.8`

As pH is less than 7, the solution is acidic.

`5.8=-log[H_3O^+]`

`[H_3O^+]=1.60* [10^(-6)M`

Thus solution is acidic and concentration of
`H_3O^+` is
`1.60* [10^(-6)M`