Which one of the following are the correct observations about acetic acid ?

Q: Which one of the following are the correct observations about acetic acid ?

Option A is correct. Acetic acid ($CH_3COOH$) is acidic in nature, which causes it to turn blue litmus paper red, and it possesses a characteristic sharp, sour smell of vinegar.

Carbon and its Compounds

Properties of Carbon Compounds

Options

(A)It turns blue litmus red and smells like vinegar

(B)It turns blue litmus red and smells like burning sulphur

(C)It turns red litmus blue and smells like vinegar

(D)It turns red litmus blue and has a fruity smell

Official Answer

Option A is correct. Acetic acid ( $CH_3COOH$ ) is acidic in nature, which causes it to turn blue litmus paper red, and it possesses a characteristic sharp, sour smell of vinegar.

acetic acidblue litmus redvinegar smellcarboxylic acid

CH_3COOH

Marking Scheme

11 mark for selecting the correct option (A).

Hint

Think about the chemical nature of carboxylic acids like acetic acid ( $CH_3COOH$ ) on indicators, and recall what common household condiment is made from dilute acetic acid.

Quick Oral Answer

Acetic acid turns blue litmus paper red because it is acidic. It has a characteristic vinegar smell because vinegar itself is a dilute solution of acetic acid in water.

Analysis & Explanation

Why A is correct: Acetic acid ( $CH_3COOH$ ) belongs to the carboxylic acid group (as shown in Table 4.3 of the text). Being an acid, it dissociates in water to release hydrogen ions, which turns blue litmus paper red. Additionally, dilute acetic acid is the primary constituent of vinegar, giving it its characteristic vinegar-like smell.
Why B is incorrect: The smell of burning sulphur is characteristic of sulphur dioxide ( $SO_2$ ), which is highly suffocating and choking, unlike the sour smell of acetic acid.
Why C is incorrect: Acids turn blue litmus red. Turning red litmus blue is a characteristic property of basic substances, not acidic ones like acetic acid.
Why D is incorrect: Acetic acid does not turn red litmus blue. Furthermore, a sweet, fruity smell is characteristic of esters, whereas acetic acid has a sharp, pungent vinegar smell.

Common Mistakes

1Confusing acetic acid with a base and selecting options that mention turning red litmus blue.
2Confusing the pungent vinegar smell of acetic acid with the sweet, fruity smell of esters.

Interesting Facts

A $5-8\%$ solution of acetic acid in water is called vinegar and is widely used as a preservative in pickles and salad dressings.

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Frequently Asked Questions

How many marks does this question carry in CBSE Class 10 Science 2012?

This question carries 1 mark in the CBSE Class 10 Science 2012 examination.

Which chapter does this question come from in Science?

This question is from the chapter "Carbon and its Compounds" in the CBSE Class 10 Science syllabus.

What topic does this question cover in Science?

This question covers the topic "Properties of Carbon Compounds" from CBSE Class 10 Science.

What type of question is this in the CBSE Class 10 Science 2012 paper?

This is a MCQ question from Section B in the CBSE Class 10 Science 2012 paper.