What is the pH of substance which has a hydronium ion concentration of 5.4 x 10-9? And what type of substance is it? (pH = -log[H3O+])

Answer:
pH = 8.2676
Type of solution: basic solution

Explanation:
Part (a) : getting the pH value:
The pH value is calculated as follows:
pH = -log [H3O]+
where:
[H3O]+ is the concentration of the hydrounium ion.
Now, we are given that the concentration of the hydronium ion = 5.4 * 10^-9
This means that:
pH = -log(5.4 * 10^-9) = 8.2676

Part (b): getting the type of the substance:
The pH scale goes as follows:
pH < 7 means that the solution is acidic
pH = 7 means that the solution is neutral
pH > 7 means that the solution is basic
For the given question, we have calculated the pH value to be equal to 8.2676
This value is greater that 7, this means that the solution is basic

Hope this helps :)