Question

Class X Sciences
[papers from previous years]

What effect does an increase in concentration of
H+ (aq.) in a solution have on the pH of
solution?

Answer 1

increase in concentration of  H⁺  hydrogen ions  will  decrease the value of  pH.  The solution will become more acidic.

pH of an aqueous solution is defined as the activity of the Hydrogen ions.   pH between 0 and 7 implies acids  and between 7 and 14 implies basic.

$pH = - Log_{10}\ [ a_{H^{+}} ] = Log_{10}\ [\frac{1}{a_{H^{+}}}]$