Question

What is the pH of a solution that has a hydrogen ion concentration of 6.9*10^-4?

Answer 1

The pH would be 3.16 because the formula for finding the pH from a H± ion is pH = -log [H±]

So with that formula, you first have to substitute the H± with your numbers which in this case is 6.9 × 10^-4.

It should like this:

pH = -log (6.9 × 10^-4)

And lastly, just calculate.

pH = 3.16

Hope that helps, do let me know if you need more help in understanding this!