JEE Chemistry Aldehydes Ketones And Carboxylic Acids MCQs Set 17

Answer: (a) ethanol

Explanation:
1. Ethanol → acetaldehyde → acetic acid, with the same carbon count.

Teacher's Note:
1. Always link acid strength to the stability of the carboxylate ion.
2. Electron-withdrawing groups increase acidity and electron-donating groups decrease it.

Answer: (c) BrCH₂CH₂COOH

Explanation:
1. A halogen close to COOH raises acidity and a more electronegative halogen raises it more.
2. The beta-Br acid has the weakest -I effect so is the weakest acid.

Teacher's Note:
1. Note the name reaction and write its equation once in your notebook.
2. Such one-step recall questions are common in the JEE and NEET style papers.

Answer: (b) BrCH₂-CH=CH₂

Explanation:
1. NBS brominates at the allylic position, giving 3-bromopropene.

Teacher's Note:
1. Count carbons before and after the reaction to avoid mistakes in chain-length changes.
2. Check whether the reagent is a reducing, oxidising or dehydrating agent before choosing the product.

Answer: (b) ethanoic acid

Explanation:
1. 2CH₃COOH → CH₃COCH₃ + CO₂ + H₂O over a metal oxide catalyst (ketonic decarboxylation).

Teacher's Note:
1. Eliminate options by checking functional groups on both sides of the reaction.
2. Only one option will have the correct functional group and carbon skeleton.

Answer: (d) Cl₃C-COOH

Explanation:
1. Three Cl atoms give the strongest -I effect and the most stable anion.

Teacher's Note:
1. Revise the physical properties such as hydrogen bonding and boiling points together with the chemistry.
2. Compare similar compounds in pairs when you are asked to rank them.

Answer: (b) liquid

Explanation:
1. Ethyl acetate boils at 77°C and is a colourless liquid with a fruity smell.

Teacher's Note:
1. Learn the reactivity order of acid derivatives: acyl chloride, anhydride, ester, amide.
2. Most questions of this type are solved by recalling the standard reagent and product pair.

Answer: (a) 1 and 4 only

Explanation:
1. Urea contains about 46 per cent N against about 21 per cent in ammonium sulphate.
2. Ammonium sulphate leaves acidic sulphate in soil, urea does not.

Teacher's Note:
1. Always link acid strength to the stability of the carboxylate ion.
2. Electron-withdrawing groups increase acidity and electron-donating groups decrease it.

Answer: (b) hydrolysis

Explanation:
1. Reaction with water that breaks the amide bond is hydrolysis.

Teacher's Note:
1. Note the name reaction and write its equation once in your notebook.
2. Such one-step recall questions are common in the JEE and NEET style papers.

Answer: (a) methanoic acid

Explanation:
1. Formic acid contains an aldehyde-like H-C(=O)- group in addition to COOH, so it is a reducing agent.

Teacher's Note:
1. Count carbons before and after the reaction to avoid mistakes in chain-length changes.
2. Check whether the reagent is a reducing, oxidising or dehydrating agent before choosing the product.

Answer: (a) trioxane

Explanation:
1. A six-membered ring of three CH2-O units is 1,3,5-trioxane.

Teacher's Note:
1. Eliminate options by checking functional groups on both sides of the reaction.
2. Only one option will have the correct functional group and carbon skeleton.

Answer: (a) two units of alcohol are obtained

Explanation:
1. RCOOR' → RCH₂OH + R'OH, giving two alcohols.

Teacher's Note:
1. Revise the physical properties such as hydrogen bonding and boiling points together with the chemistry.
2. Compare similar compounds in pairs when you are asked to rank them.

Answer: (d) methyl iodide and phenol

Explanation:
1. HI protonates the ether oxygen, and I- attacks the methyl carbon (the aryl C-O bond does not break).
2. Products: CH₃I and C₆H₅OH.

Teacher's Note:
1. Learn the reactivity order of acid derivatives: acyl chloride, anhydride, ester, amide.
2. Most questions of this type are solved by recalling the standard reagent and product pair.

Answer: (b) a hydrocarbon is formed

Explanation:
1. The Grignard reagent acts as a base and removes the acidic H: CH₃COOH + CH₃MgX → CH₃COOMgX + CH₄.

Teacher's Note:
1. Always link acid strength to the stability of the carboxylate ion.
2. Electron-withdrawing groups increase acidity and electron-donating groups decrease it.

Answer: (b) carboxylic acids

Explanation:
1. Carboxylic acids form strong hydrogen-bonded dimers, so they have higher boiling points than alcohols of similar mass.

Teacher's Note:
1. Note the name reaction and write its equation once in your notebook.
2. Such one-step recall questions are common in the JEE and NEET style papers.

Answer: (d) ethylamine

Explanation:
1. The Hofmann bromamide reaction removes the carbonyl carbon, so the amine has one carbon fewer.
2. Propanamide gives ethylamine.

Teacher's Note:
1. Count carbons before and after the reaction to avoid mistakes in chain-length changes.
2. Check whether the reagent is a reducing, oxidising or dehydrating agent before choosing the product.

Answer: (b) methyl ethanoate

Explanation:
1. Kolbe electrolysis of CH₃COO- gives C₂H₆, so the acid is ethanoic acid.
2. Methyl ethanoate gives acetic acid on hydrolysis.

Teacher's Note:
1. Eliminate options by checking functional groups on both sides of the reaction.
2. Only one option will have the correct functional group and carbon skeleton.

Answer: (c) biuret

Explanation:
1. Urea above its melting point loses NH₃ to form biuret, H₂NCONHCONH₂.

Teacher's Note:
1. Revise the physical properties such as hydrogen bonding and boiling points together with the chemistry.
2. Compare similar compounds in pairs when you are asked to rank them.

Answer: (a) ethanolic KOH

Explanation:
1. Ethanolic KOH removes the acidic N-H, giving potassium phthalimide.
2. This then reacts with the alkyl halide.

Teacher's Note:
1. Learn the reactivity order of acid derivatives: acyl chloride, anhydride, ester, amide.
2. Most questions of this type are solved by recalling the standard reagent and product pair.

Answer: (d) FCH₂COOH

Explanation:
1. F is the most electronegative halogen and gives the largest -I effect.

Teacher's Note:
1. Always link acid strength to the stability of the carboxylate ion.
2. Electron-withdrawing groups increase acidity and electron-donating groups decrease it.

Answer: (d) formic acid

Explanation:
1. Formic acid has an aldehyde-type H and reduces Ag+ to silver.

Teacher's Note:
1. Note the name reaction and write its equation once in your notebook.
2. Such one-step recall questions are common in the JEE and NEET style papers.

Answer: (b) ammoniacal silver nitrate solution

Explanation:
1. Both acids turn litmus red and liberate CO₂ from bicarbonate.
2. Tartaric acid, with its alpha-hydroxy groups, reduces ammoniacal silver nitrate, while oxalic acid does not.

Teacher's Note:
1. Count carbons before and after the reaction to avoid mistakes in chain-length changes.
2. Check whether the reagent is a reducing, oxidising or dehydrating agent before choosing the product.

Answer: (b) CO

Explanation:
1. Conc. H₂SO₄ dehydrates formic acid: HCOOH → CO + H₂O.

Teacher's Note:
1. Eliminate options by checking functional groups on both sides of the reaction.
2. Only one option will have the correct functional group and carbon skeleton.

Answer: (b) m-sulphobenzoic acid

Explanation:
1. COOH is electron-withdrawing and meta-directing.

Teacher's Note:
1. Revise the physical properties such as hydrogen bonding and boiling points together with the chemistry.
2. Compare similar compounds in pairs when you are asked to rank them.

Answer: (d) CHF₂COOH

Explanation:
1. Two fluorines give the greatest -I effect.
2. F has a stronger effect than Cl, and two halogens beat one.

Teacher's Note:
1. Learn the reactivity order of acid derivatives: acyl chloride, anhydride, ester, amide.
2. Most questions of this type are solved by recalling the standard reagent and product pair.

Answer: (c) CH₃COOH

Explanation:
1. Acetic acid lacks a reducing aldehyde-type group.

Teacher's Note:
1. Always link acid strength to the stability of the carboxylate ion.
2. Electron-withdrawing groups increase acidity and electron-donating groups decrease it.

Answer: (c) CH₃COCH₃

Explanation:
1. Ketonic decarboxylation: 2CH₃COOH → CH₃COCH₃ + CO₂ + H₂O.

Teacher's Note:
1. Note the name reaction and write its equation once in your notebook.
2. Such one-step recall questions are common in the JEE and NEET style papers.

Answer: (b) it has a lower degree of ionisation

Explanation:
1. Acetic acid ionises only partly in water, whereas sulphuric acid ionises almost completely.

Teacher's Note:
1. Count carbons before and after the reaction to avoid mistakes in chain-length changes.
2. Check whether the reagent is a reducing, oxidising or dehydrating agent before choosing the product.

Answer: (c) more acidic

Explanation:
1. The methyl group of acetic acid donates electrons (+I effect) and destabilises the anion, so formic acid is stronger.

Teacher's Note:
1. Eliminate options by checking functional groups on both sides of the reaction.
2. Only one option will have the correct functional group and carbon skeleton.