Question

What is the ph of an aqueous solution at 25.0 °c that contains 3.98 ⋅ 10-9 m hydronium ion? what is the ph of an aqueous solution at 25.0 °c that contains 3.98 10-9 m hydronium ion? 5.600 9.000 8.400 7.000 3.980?

Answer 1

pH scale tells how acidic or basic a solution is, at 25 °C, if pH > 7 - basic , 
pH = 7 neutral and if pH < 7 then its an acidic solution.
pH can be calculated as follows;
pH = - log[H₃O⁺]
pH = - log (3.98 x 10⁻⁹ M)
pH = 8.400 
therefore pH of the solution is 8.400