Calculating Hydronium Concentration Using pH

This problem requires that you rearrange the pH equation and solve for the [H3O+]. Because 4.0 has one digit to the right of the decimal, the answer must have one significant figure. 

CHECK YOUR WORK A solution with a pH of 4.0 is acidic. The answer, 1 x 10 4 m, is greater than 1.0 X 10 M, which is correct for an acidic solution. J 

This problem is very similar to previous pH problems. You will need to substitute values into the pH = —log [H3O+] equation and use a calculator. Once the [H3O+] is determined, the ion-product constant [H3O+] [OH ] = 1.0 x 10 maybe used to calculate [OH ]. 

A pH of 7.52 is slightly greater than a pH of 7. This means that the solution is slightly basic. 

Because the solution is slightly basic, a hydroxide ion concentration slightly larger than 10 M is predicted. A hydronium ion concentration slightly less than 10 M is also predicted. The answers agree with these predictions. 

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