Question

A student tests the pH of pure water using a pH paper. It shows the green color. If a pH paper is used after adding lemon juice to water, what color will be observed?
(a)- Green
(b)- Red
(c)- Yellow
(d)- Purple

Answer 1

Hint: The color ranges on the pH paper are Red, orange, yellow, green, blue, purple, and violet. In the pure water, it was green, which means that green indicates the neutral compound. If the solution becomes acidic then the colors will be from red, orange, or yellow, and if the solution is basic then the colors will be blue, purple, or violet.

Complete answer:
The color ranges on the pH paper are Red, orange, yellow, green, blue, purple, and violet. As we know that the pH paper is used to indicate the compounds' nature, i.e., acidic, basic, or neutral character.
In the pure water, it was green, which means that green indicates the neutral compound. If the solution becomes acidic then the colors will be red for strongly acidic, orange for medium acidic, or yellow for mild acidic, and if the solution is basic then the colors will be blue for mild basic, purple for medium basic, or violet for a strongly basic solution.
When the lemon juice is added to water then the solution will become slightly acidic because lemon juice contains citric acid which on dissolution in water will release hydrogen ions and make the solution acidic. But citric acid is a weak acid, it gives only yellow color on the pH paper.

Therefore, the correct answer is an option (c)- Yellow.

Note:
Some of the compounds that will give red on the pH paper are hydrochloric acid, sulfuric acid, nitric acid, etc while some of the compounds that will give violet color on the pH paper are sodium hydroxide, potassium hydroxide, etc.