The pH of a solution is 7. When acid is added to the solution, the hydronium ion concentration becom


The pH of a solution is 7. When acid is added to the solution, the hydronium ion concentration becomes 100 times greater. What is the pH of the new solution?

(1) 1

(2) 5

(3) 9

(4) 14

Answer and Explanation:

First we need to understand the pH scale well. If pH less than 7, the solution is acid, equal to 7 is neutral and greater than 7 is basic. When acid is added to the solution, it should become more acidic and therefore have a lower pH.Every time the concentration of Hydrogen ion increases by 10, that equal to going 1 unit down on the pH scale. Therefore if the hydrogen ion concentration increases by 100, the pH of the solution should be 2 units lower than the original ph. 7-2= 5. The new pH is 5, choice (2).

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