Hydronium ion : How to find concentration of hydronium ion from pH

hey

The usefulness of the pH scale depends on the case with which you can interconvert pH and hydrogen ion concentration.lets see a solved example:

Sample problem 1 : The pH of arterial human blood is 7.40 .What is hydrogen in concentration?

Solution:
Step1: the pH = - log [H+]

So, hydrogen ion concentration is [H+] = antilog (-pH) = 10^-pH

Step2 : On some calculators,you obtain the anti logarithm by taking the inverse of the logarithm .On others,you use a 10x key.

Step3: the results is [H+]= antilog(-7.40)= 10^-7.40 = 4.0 x 10-8 M