Question

Question 7(Multiple Choice Worth 4 points)

(08.05 MC)

What is the pH of a solution with a 3.8 × 10−4 M hydronium ion concentration?

3.4
3.8
11
12

Answer 1

The pH of this solution is 3.4.

Step-by-step explanation:

Consider the definition of the pH of a solution:

`\displaystyle \rm pH = \log{(1)/([H_(3)O^(+)])} = - \log{[H_3O}^(+)]}`,

where

• 
  `\rm [H_3O}^(+)]` is the hydronium ion concentration of the solution in moles per liter. Note that some textbooks write
  `\rm [H_3O}^(+)]` as
  `\rm H^(+)`.

The unit "M" here is the same as moles per liter.

On a scientific calculator, evaluate

`\rm -\log{(3.8* 10^(-4))}`

to find the pH of this solution.

`\rm pH = -\log{(3.8* 10^(-4))} \approx 3.4`.

The pH of this solution is approximately 3.4.