MCQ
Q.
Turmeric stains on the shirt turn red when washed with soap because ________.
Correct Answer: D
The correct answer is Soap solution is alkaline.
Concept:
- Indicators are the substances that are used to identify whether the given substance is an acid or a base.
- There are two types of indicators:
- Natural: These indicators are obtained from natural sources like plants.
- Turmeric, litmus, china rose petals, etc., are some of the naturally occurring indicators.
- The most commonly used natural indicator is litmus.
- It is extracted from lichens.
- It is available in the form of a solution, or in the form of strips of paper, known as litmus paper.
- Generally, it is available as red and blue litmus paper.
- Man-made: Phenolphthalein, Methyl orange are some of the man-made indicators.
Explanation:
-
- The indicators change their colour when added to a solution containing an acidic or a basic substance.
- Turmeric is a natural indicator. It contains the substance
curcumin which changes colour with pH.
- When a substance is basic, the colour is red, whereas when the substance is acidic, the colour of turmeric turns yellow to brown
- Turmeric stains on the shirt turn red when washed with soap because the soap solution is basic in nature which changes the yellow colour of Turmeric into red colour.
- It is because turmeric contains tartaric acid, while the soap contains a sodium hydroxide base. When an acid reacts with a base, a neutralization reaction takes place and the stain becomes neutral.
Neutralization Reaction
- A neutralization reaction can be defined as a chemical reaction in which an acid and base quantitatively react together to form salt and water as products.
Saponification
- Saponification is the hydrolysis of an ester with NaOH or KOH to give alcohol and sodium or potassium salt of the acid.
