- A highly acidic solution has a pH equal to zero. - A highly alkaline solution has a pH of 14. - A weak acid has a pH of not less than 7 . - A neutral solution has a pH of 7 . - The word pH stands for "pondus Hydrogenium". The pH isdetermined by the number of free hydrogen ions (H+) and hydroxide (OH−) ions in a substance. - When the number of hydrogen ions is higher ion a solution then the solution is acidic. - When the number of hydroxide ions is higher iona solution then the solution is basic.