Question

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.Antacid

Answer 1

Hint:Acids are substances which when added to litmus paper turns the litmus paper to red and the basic or alkaline solutions when added to the litmus paper turns it into blue colour. So the solution which will be basic in nature will turn the pH paper to blue.

Complete step by step answer:According to the question the solution of water and soil is acidic in nature as it is able to turn the litmus paper into yellow-orange colour.
We will discuss each option and their possibility of turning the litmus papers colour.
Lemon juice: we know that lemon is a rich source of vitamin C, which is known as citric acid. Being a weak acid it will be able to turn the litmus towards the range of red.
Vinegar: it is a combination of water and acetic acid. It acts as a mild acid and it also turns the litmus paper towards the red range.
Common salt: it is used commonly in our homes. It includes the sodium and chloride ions and is not able to turn the litmus to blue as it is not a basic compound.
Antacid: It has its neutralizing property for acids in our stomach. It reduces the acidity with the alkaline nature of its compounds such as aluminium and sodium carbonate.

Thus the correct option is D, as it is an alkaline substance and only base can turn the yellow litmus to orange.


Note: pH is one of the important properties in categorizing the substances and their solutions. The acids have the pH range from 0-6, base or alkali have the pH range from 7-14 and the substances at pH 7 are neutral like water.