Organic Chemistry D. Organic Acids

1. Assertion (A): Formic Acid is a stronger acid than Acetic acid. [I.A.S. (Pre) 1998]

Reason (R): Formic Acid is an organic acid.
Code:

(a) Both (A) and (R) are true and (R) is the correct explanation of (A).
(b) Both (A) and (R) are true but (R) is not correct explanation of (A).
(c) (A) is true but (R) is false.
(d) (A) is false but (R) is true.

Correct Answer: (b) Both (A) and (R) are true but (R) is not correct explanation of (A).

Solution:Formic acid (HCOOH) and acetic acid (CH₃COOH) both are organic acids. Acetic acid contains an electron donating methyl group (CH₃). While formic acid has no such electron donating group and hence it is stronger acid than acetic acid.

2. Which acid is described as HOOC-COOH? [68th B.P.S.C. (Pre) 2022]

Correct Answer: (b) Oxalic acid

Solution:Oxalic acid is a dicarboxylic acid with a chemical formula C₂H₂O₄, also written as (COOH)₂ or (CO₂H)₂. It is also known as Ethanedioic acid or Oxiric acid. This organic compound is found in many vegetables and plants. It is the simplest dicarboxylic acid with condensed formula HOOC-COOH and has an acidic strength greater than acetic acid.

3. The sensation of fatigue in the muscles after prolonged strenuous physical work is caused by – [I.A.S. (Pre) 2000]

(a) A decrease in the supply of oxygen
(b) Minor wear and tear of muscle fibres
(c) The depletion of glucose
(d) The accumulation of lactic acid

Correct Answer: (d) The accumulation of lactic acid

Solution:After hard physical work, if oxygen supply to muscles is insufficient (anaerobic conditions), glucose is metabolized into pyruvate, which is then converted to lactate (lactic acid) to regenerate

N A D^{+}

for glycolysis to continue producing ATP. due to the accumulation of lactic acid (CH₃CH(OH)CO₂H) in muscles, leads to a drop in pH, inhibiting muscle contraction and the body would experience fatigue. The rapid accumulation of lactic acid is not a temporary process. Rest is needed to remove tiredness. A body massage also helps to get relief from fatigue.

4. Accumulation of which one of the following in the muscles leads to fatigue? [U.P. P.C.S. (Pre) 2010 ,U.P. Lower Sub. (Spl.) (Pre) 2008, U.P.P.C.S. (Pre) 1992]

(a) Lactic acid
(b) Benzoic acid
(c) Pyruvic acid
(d) Uric acid

Correct Answer: (a) Lactic acid

Solution:After hard physical work, due to the accumulation of lactic acid (CH₃CH(OH)CO₂H) in muscles, the body would experience fatigue. The rapid accumulation of lactic acid is not a temporary process. Rest is needed to remove tiredness. A body massage also helps to get relief from fatigue.

5. Which acid accumulates in the muscles to cause fatigue? [Chhattisgarh P.C.S. (Pre) 2013]

(a) Lactic acid
(b) Pyruvic acid
(c) Citric acid
(d) Uric acid

Correct Answer: (a) Lactic acid

Solution:After hard physical work, due to the accumulation of lactic acid (CH₃CH(OH)CO₂H) in muscles, the body would experience fatigue. The rapid accumulation of lactic acid is not a temporary process. Rest is needed to remove tiredness. A body massage also helps to get relief from fatigue.

6. Lemon is citrus due to – [39th B.P.S.C. (Pre) 1994]

(a) Hydrochloric acid
(b) Acetic acid
(c) Tartaric acid
(d) Citric acid

Correct Answer: (d) Citric acid

Solution:Lemon contains mainly citric acid (C₆H₈O₇), which fulfills the deficiency in the body. Citric acid is a weak organic acid found in citrus fruits. Citric acid is most concentrated in lemons and limes, where it can comprise as much as 8% of the dry weight of the fruit. Acetic acid is found in vinegar, while tartaric acid is found in tamarind.

7. Which acid is mainly found in lemons? [M.P.P.C.S. (Pre) 2003]

(a) Acetic acid
(b) Ascorbic acid
(c) Citric acid
(d) Nitric acid

Correct Answer: (c) Citric acid

Solution:Lemon contains mainly citric acid (C₆H₈O₇), which fulfills the deficiency in the body. Citric acid is a weak organic acid found in citrus fruits. Citric acid is most concentrated in lemons and limes, where it can comprise as much as 8% of the dry weight of the fruit.

Ascorbic acid: Also known as Vitamin C, found in lemons but not the main acid responsible for its citrus taste.

Acetic acid: Found in vinegar.

Nitric acid: A strong mineral acid.

8. Table: Match List-I and List-II and select the correct answer from the code given below: [U.P.P.C.S. (Pre) 1997]

List-I (Acid)	List-II (Source)
A. Lactic acid	1. Lemon
B. Acetic acid	2. Rancid butter
C. Citric acid	3. Milk
D. Butyric acid	4. Vinegar

Code:

Code	A	B	C	D
(a)	1	4	3	2
(b)	1	2	3	4
(c)	2	3	4	1
(d)	3	4	1	2

(a)
(b)
(c)
(d)

Correct Answer: (d)

Solution:Lactic acid is found in milk, acetic acid is found in vinegar, citric acid is found in lemon, and butyric acid is found in rancid butter.

9. Table: Match List-I with List-II and select the correct answer from the code given below the lists:

List-I	List-II
A. Acetic Acid	1. Butter
B. Lactic acid	2. Lemon
C. Butyric acid	3. Vinegar
D. Citric acid	4. Milk

Code	A	B	C	D
(a)	3	4	2	1
(b)	3	4	1	2
(c)	4	2	3	1
(d)	1	2	3	4

(a)
(b)
(c)
(d)

Correct Answer: (b)