All Free Biology MCQs with Answers
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19844 questions · page 514 of 1985
5131. Which of the following halosubstituted carboxylic acids is the strongest acid?
- A. FCH2COOH
- B. CICH2COOH
- C. BrCH2COOH
- D. ICH2COOH
Explanation: Fluorine is the most electronegative halogen. The electron-withdrawing effect of fluorine increases the acidity of the carboxylic acid by stabilizing the conjugate base. Thus, fluoroacetic acid is the strongest acid among the options provided.
Correct answer: FCH2COOH5132. Organic compounds X and Y react together to form organic compound (Z). What type of compounds X, Y and Z be?
- A. Option A
- B. Option B
- C. Option C
- D. Option D
Explanation: The reaction of acid and alcohol gives ester.
Correct answer: Option D5133. Vinegar has:
- A. 1 to 10 % ethanoic acid
- B. 10 to 20 % ethanoic acid
- C. 100 % ethanoic acid
- D. 30 to 40 % ethanoic acid
Explanation: This range represents the typical concentration of ethanoic acid, or acetic acid, found in vinegar. Vinegar is a dilute solution of acetic acid in water, commonly ranging from 4% to 8% concentration.
Correct answer: 1 to 10 % ethanoic acid5134. Rancid butter has the smell due to:
- A. Butanoic acid
- B. Propanoic acid
- C. Ethanoic acid
- D. Methanoic acid
Explanation: Rancid butter typically has a smell due to the presence of butanoic acid, also known as butyric acid. This compound is responsible for the characteristic unpleasant odor often associated with rancid butter.
Correct answer: Butanoic acid5135. Carbosylic acids have greater melting and boiling points than alcohols because they have stronger?
- A. Hydrogen bonding
- B. Dispole-dispole forces
- C. Debye forces
- D. Van Der Waals forces
Explanation: Carboxylic acids can form strong hydrogen bonds due to the presence of the carboxyl group (-COOH). This allows molecules of carboxylic acids to attract each other more strongly, resulting in higher melting and boiling points compared to alcohols, which primarily rely on weaker dipole-dipole forces.
Correct answer: Hydrogen bonding5136. Mark the Incorrect statement about structure of formic acid:
- A. It has planar structure
- B. The bond length C = O is 120 pm
- C. The bond angle of H - C = O is 124o
- D. The bond angle of O - C = O is 120
Explanation: The bond angle of O-C=O in formic acid is indeed approximately 120 degrees.
Correct answer: The bond angle of O - C = O is 1205137. The monocarboxylic acids are monobasic acids. Which of the following is resonance hybrid structure of carboxylate ion?
- A. Option A
- B. Option B
- C. Option C
- D. Option D
Explanation: The carboxylate ion, which is the conjugate base of a carboxylic acid, can be represented by two resonance structures. The resonance hybrid structure is a combination of these two structures and is depicted as follows:O||C-O⁻The negative charge is delocalized over both oxygen atoms, leading to a more stable structure than either resonance contributor alone.
Correct answer: Option C5138. Which of the followings has comparatively less acidic character?
- A. Ethanoic acid
- B. Ethanol
- C. Phenol
- D. Water
Explanation: Ethanol is correct because ethanol is less acidic compared to the other options listed.
Correct answer: Ethanol5139. Which of the following is not derivative of carboxylic acid?
- A. Alkanoyl chloride
- B. Alkyl alkanoate
- C. Alkane amides
- D. Alkanal
Explanation: Unlike the other options, alkanals are not derivatives of carboxylic acids. Alkanals, also known as aldehydes, are organic compounds containing a carbonyl group (C=O) bonded to a hydrogen atom and an alkyl or aryl group. The general formula for an alkanal is RCHO, where R represents an alkyl or aryl group. Aldehydes are important intermediates in organic synthesis and are found in various natural products and industrial processes.
Correct answer: Alkanal5140. Which class of organic compounds is used for artificial flavorings in jams?
- A. Ester
- B. Carboxylic acid
- C. Ketone
- D. Aldehydes
Explanation: Esters are commonly used as artificial flavorings in jams. As mentioned earlier, esters have a pleasant fruity aroma and taste, making them ideal for enhancing the flavor of jams and other food products.
Correct answer: Ester