Organic Acid

1. Which one of the following does NOT contain COOH group ?

Which one of the following does NOT contain COOH group ?

Citric acid
Lactic acid
Tartaric acid
Ascorbic acid
This question was previously asked in
UPSC CAPF – 2019
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The correct option is D.
The question asks which of the listed compounds does NOT contain a carboxylic acid group (-COOH). Citric acid (C₆H₈O₇) contains three -COOH groups. Lactic acid (C₃H₆O₃) contains one -COOH group and one hydroxyl (-OH) group. Tartaric acid (C₄H₆O₆) contains two -COOH groups and two -OH groups. Ascorbic acid (C₆H₈O₆), also known as Vitamin C, is a weak acid, but its acidity primarily arises from enol groups, not carboxylic acid groups. Its structure is based on a lactone ring and does not contain a -COOH functional group.
Citric acid is found in citrus fruits. Lactic acid is produced in muscles during strenuous exercise and found in sour milk. Tartaric acid is found in grapes and tamarinds. Ascorbic acid is a vital nutrient found in fruits and vegetables, essential for various metabolic processes.

2. Which of the following statements about carboxylic acids is/are correc

Which of the following statements about carboxylic acids is/are correct?

  • 1. Simple aliphatic carboxylic acids are soluble in water.
  • 2. Higher carboxylic acids are practically insoluble in water.
  • 3. The acidity of a carboxylic acid depends on the number of carbon atoms present in the hydrocarbon chain.

Select the correct answer using the code given below.

1 and 2 only
2 and 3 only
1 only
1, 2 and 3
This question was previously asked in
UPSC CAPF – 2018
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All three statements about carboxylic acids are correct.
1. Simple aliphatic carboxylic acids (e.g., formic acid, acetic acid) are soluble in water because the polar carboxyl group (-COOH) can form hydrogen bonds with water molecules.
2. As the hydrocarbon chain length increases in higher carboxylic acids, the nonpolar hydrophobic part dominates, making them practically insoluble in water.
3. The acidity of a carboxylic acid is related to the stability of its conjugate base (carboxylate ion). Alkyl groups are electron-donating, which destabilizes the negative charge on the carboxylate ion. Therefore, increasing the number of carbon atoms (length of the alkyl chain) generally decreases the acidity of aliphatic carboxylic acids. The hydrocarbon chain’s size *does* influence acidity.
Conversely, electron-withdrawing groups (like halogens, nitro groups) attached to the hydrocarbon chain increase the acidity by stabilizing the conjugate base through inductive effects or resonance. For aromatic carboxylic acids (like benzoic acid), substituents on the ring also affect acidity.

3. Bee sting leaves an acid which causes pain and irritation. The acid re

Bee sting leaves an acid which causes pain and irritation. The acid released is

tartaric acid
citric acid
ethanoic acid
methanoic acid
This question was previously asked in
UPSC NDA-2 – 2022
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The correct answer is methanoic acid.
Bee sting venom contains several substances, including formic acid, which is also known as methanoic acid (HCOOH). This acid is primarily responsible for the pain and irritation experienced from a bee sting.
While bee venom contains various components, including peptides and enzymes, formic acid is the key acidic component causing the immediate stinging sensation. Wasp stings, in contrast, are alkaline.

4. Vinegar is also known as

Vinegar is also known as

ethanoic acid
nitric acid
sulphuric acid
tartaric acid
This question was previously asked in
UPSC NDA-2 – 2020
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Vinegar is primarily an aqueous solution of acetic acid, which is also known by its IUPAC name, ethanoic acid.
– Acetic acid (CH₃COOH) is a weak organic acid.
– Culinary vinegar typically contains 5% to 8% acetic acid by volume.
– Acetic acid is produced industrially and also biologically by the fermentation of ethanol by acetic acid bacteria.
– It is widely used in cooking, as a preservative, and for cleaning purposes.

5. The main constituent of Vinegar is:

The main constituent of Vinegar is:

Acetic acid
Ascorbic acid
Citric acid
Tartaric acid
This question was previously asked in
UPSC NDA-2 – 2015
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The correct answer is A) Acetic acid.
Vinegar is primarily an aqueous solution of acetic acid. Typically, it contains 5-20% acetic acid by volume. Acetic acid is responsible for vinegar’s characteristic sour taste and pungent smell.
Other options are incorrect. Ascorbic acid is Vitamin C. Citric acid is found in citrus fruits. Tartaric acid is found in grapes and tamarinds. While small amounts of other acids may be present depending on the production method, acetic acid is the main constituent.

6. Which one among the following is present in the nettle leaf hairs that

Which one among the following is present in the nettle leaf hairs that causes burning pain ?

Methanoic acid
Ethanoic acid
Benzoic acid
Acetic acid
This question was previously asked in
UPSC NDA-1 – 2024
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Methanoic acid is present in nettle leaf hairs and causes a burning pain.
The stinging hairs (trichomes) of nettle plants contain several irritants, including histamine, acetylcholine, serotonin, and an acid. The primary acid responsible for the burning and stinging sensation is formic acid, also known by its IUPAC name, methanoic acid (HCOOH).
Ethanoic acid is acetic acid (CH₃COOH), found in vinegar. Benzoic acid (C₆H₅COOH) is an aromatic carboxylic acid. While other chemicals contribute, methanoic acid is the key acidic component causing the initial sting.

7. Which one of the following acids is predominantly found in tomatoes ?

Which one of the following acids is predominantly found in tomatoes ?

Acetic acid
Tartaric acid
Oxalic acid
Lactic acid
This question was previously asked in
UPSC NDA-1 – 2021
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Tomatoes contain several organic acids, including citric acid, malic acid, and oxalic acid. While citric acid is often the most abundant overall acid, tomatoes are a particularly significant source of oxalic acid compared to many other common fruits and vegetables. Among the options provided, oxalic acid is the predominant one found in notable quantities in tomatoes.
Oxalic acid is a dicarboxylic acid (COOH-COOH) found in many plants. Acetic acid is the primary component of vinegar. Tartaric acid is found in grapes and tamarind. Lactic acid is produced during fermentation (e.g., in yogurt) and in muscles during strenuous exercise.
The presence of oxalic acid contributes to the tangy taste of tomatoes. While important for understanding nutritional content and potential interactions (like with calcium), it’s worth noting that the relative abundance of acids can vary slightly depending on the tomato variety and ripeness.

8. Which one of the following is an organic acid ?

Which one of the following is an organic acid ?

Hydrochloric acid
Nitric acid
Acetic acid
Sulphuric acid
This question was previously asked in
UPSC NDA-1 – 2019
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Organic acids are typically organic compounds that contain acidic properties. The most common type of organic acid is a carboxylic acid, which contains a carboxyl group (-COOH). Among the given options, Acetic acid (CH₃COOH) is an organic compound containing a carboxyl group and is therefore an organic acid.
– Hydrochloric acid (HCl) is a strong inorganic acid (mineral acid).
– Nitric acid (HNO₃) is a strong inorganic acid (mineral acid).
– Acetic acid (CH₃COOH) is a carboxylic acid and a weak organic acid. It is the main component of vinegar.
– Sulphuric acid (H₂SO₄) is a strong inorganic acid (mineral acid).
Inorganic acids are typically derived from inorganic compounds and often do not contain carbon (with a few exceptions like carbonic acid, H₂CO₃). Organic acids are carbon-based compounds, typically derived from living organisms or their products.

9. Stung by hairs of nettle leaves causes burning pain. This is due to th

Stung by hairs of nettle leaves causes burning pain. This is due to the injection of

Acetic acid
Methanoic acid
Sulphuric acid
Hydrochloric acid
This question was previously asked in
UPSC NDA-1 – 2017
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The burning pain caused by stinging hairs of nettle leaves is primarily due to the injection of chemicals including formic acid, also known by its systematic name methanoic acid (HCOOH). Other irritants like histamine, acetylcholine, and serotonin are also present, but methanoic acid is a key contributor to the stinging sensation.
Methanoic acid (formic acid) is responsible for the stinging pain from nettle hairs.
Applying a weak base, such as a solution of baking soda or rubbing the affected area with the leaves of docks (often found growing near nettles), can help neutralize the acid and relieve the pain.

10. Which one of the following sources contains tartaric acid ?

Which one of the following sources contains tartaric acid ?

Lemon juice
Orange juice
Tamarind paste
Vinegar
This question was previously asked in
UPSC Geoscientist – 2024
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Tamarind paste is a significant source of tartaric acid.
Tartaric acid is one of the principal acids found in tamarind, contributing to its characteristic sour taste.
Lemon juice and orange juice are rich in citric acid. Vinegar primarily contains acetic acid. Tartaric acid is also found naturally in grapes, bananas, and citrus fruits, but tamarind contains particularly high concentrations. It is also used as a food additive (E334) for its antioxidant and acidic properties.
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