question_answer 25)

                  A sample of soil is mixed with water and allowed to settle. The clear supernatant solution turns the pH paper yellowish-orange. Which of the following would change the colour of this pH paper to greenish-blue?             (a) Lemon juice         (b) Vinegar                    (c) Common salt               (d) An antacid           

Answer:

  (d) As pH paper turns greenish blue for weakly basic compound and antacids contain weak base like Mg(OH)2. So, an antacid would change the colour of this pH paper to greenish-blue. Other options (a) and (b) contain acids and option (c) is a neutral salt.