Vinegar is also known as
- (a)ethanoic acid
- (b)nitric acid
- (c)sulphuric acid
- (d)tartaric acid
Correct — A, ethanoic acid. Vinegar is a dilute (about 4-8%) aqueous solution of acetic acid, whose systematic (IUPAC) name is ethanoic acid, CH3COOH. It is a weak organic acid that gives vinegar its sour taste and pungent smell.
- (b)nitric acid — Nitric acid (HNO3) is a strong, corrosive mineral acid used in industry and explosives, far too aggressive to be vinegar.
- (c)sulphuric acid — Sulphuric acid (H2SO4) is a strong, dehydrating mineral acid, not an edible food substance.
- (d)tartaric acid — Tartaric acid occurs in grapes and tamarind and is used in baking powder, but it is not what vinegar is made of.
Ethanoic acid (acetic acid), CH3COOH, is the simplest carboxylic acid in everyday use; a dilute solution of it is household vinegar. 'Ethanoic' is the IUPAC name and 'acetic' the traditional name for the very same compound.
The trap options are two strong mineral acids and another edible acid. Since vinegar is a mild, sour, edible liquid, only the weak organic acid — ethanoic (acetic) acid — fits.
- Vinegar is a dilute solution of acetic (ethanoic) acid, CH3COOH.
- Ethanoic acid is the IUPAC name; acetic acid is the common name for the same substance.
- It is a weak carboxylic acid.
- Glacial acetic acid is the pure, water-free form and freezes near 17 degrees Celsius.
- Picking a strong mineral acid such as sulphuric or nitric acid.
- Not realising that ethanoic acid and acetic acid are the same compound.
Asked by naming a common substance (vinegar) and requiring its chemical identity.
When ants bite, they inject
- (a) glacial acetic acid
- (b) methanol
- (c) formic acid
- (d) stearic acid
Answer(c) formic acid
Same theme of everyday weak organic acids — vinegar is ethanoic (acetic) acid, while an ant's sting injects formic acid; note glacial acetic acid appears here as a distractor.
Which one among the following is present in the nettle leaf hairs that causes burning pain?
- (a) Methanoic acid
- (b) Ethanoic acid
- (c) Benzoic acid
- (d) Acetic acid
Answer(a) Methanoic acid
Same 'identify the everyday organic acid' idea; the stinging nettle contains methanoic (formic) acid, while vinegar is ethanoic (acetic) acid — close cousins among carboxylic acids.
- practice — not a real PYQ
The common name of ethanoic acid is
- (a)citric acid
- (b)acetic acid
- (c)formic acid
- (d)lactic acid
Answer(b) acetic acid — the same compound found in vinegar.
- practice — not a real PYQ
Which acid is naturally present in citrus fruits such as lemon and orange?
- (a)acetic acid
- (b)citric acid
- (c)tartaric acid
- (d)formic acid
Answer(b) citric acid.