We know that, the pH value of a solution is equal to the negative power to which 10 must be raised in order to express H+ ion concentration, i.e., [H+]=10−pH The pH of a solution is the negative logarithm of its H+ ion concentration. pH=−log[H+] The pH of a solution is logarithm of the reciprocal of H+ ion concentration. pH=log
1
[H+]
Now, [H+]=[OH−]=1×10−7,pH=7 In an acidic solution [H+]>10−7 pH is less than 7 In an alkaline solution [H+]<10−7,pH is greater than 7 . So, an aqueous solution in which the H+ ion concentration is greater than 10−7M, the solution is acidic.