MDCAT ECAT Chemistry MCQs with Answers – All Units – Page 5

Question 81 Alkyl Halides

Heating bromoethane with aqueous KOH mainly produces ____.

Correct answer A. ethanol

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Question 82 Alkyl Halides

What is the rate law for an E1 elimination of an alkyl halide RX by a base?

Correct answer B. Rate = k[RX]

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Question 83 Alkyl Halides

What is the approximate percentage by mass of bromine in bromoethane, C₂H₅Br (C = 12, H = 1, Br = 80)?

Correct answer C. 73.4%

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Question 84 Alkyl Halides

Bromoethane reacts with potassium cyanide to give ____.

Correct answer D. propanenitrile

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Question 85 Alkyl Halides

What is the correct order of reactivity of alkyl bromides in SN2 reactions?

Correct answer A. Methyl > primary > secondary > tertiary

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Question 86 Alcohols and Phenols

What is the IUPAC name of CH₃CH(OH)CH₃?

Correct answer A. Propan-2-ol

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Question 87 Fundamental Principles of Organic Chemistry

What is the name of the functional group present in CH₃CONH₂?

Correct answer D. Amide

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Question 88 Fundamental Principles of Organic Chemistry

The functional group −COOR is characteristic of which class of compounds?

Correct answer B. Esters

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Question 89 Fundamental Principles of Organic Chemistry

Ethanol and dimethyl ether are an example of which type of isomerism?

Correct answer B. Functional group isomerism

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Question 90 Transition Elements

The Cu⁺ ion forms mostly colourless compounds because it has ____.

Correct answer C. a completely filled 3d¹⁰ subshell

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Question 91 Fundamental Principles of Organic Chemistry

Which of these compounds is usually NOT classified as an organic compound?

Correct answer D. Calcium carbonate

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Question 92 Fundamental Principles of Organic Chemistry

Which of these is a heterocyclic compound?

Correct answer C. Pyridine

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Question 93 Fundamental Principles of Organic Chemistry

Open-chain organic compounds are also known as ____ compounds.

Correct answer C. acyclic

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Question 94 Chemical Bonding

How is a sigma (σ) bond formed?

Correct answer A. By head-on (end-to-end) overlap of orbitals along the internuclear axis

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Question 95 Chemical Bonding

How many sigma and pi bonds are present in a benzene molecule, C₆H₆ (Kekulé structure)?

Correct answer D. 12 sigma and 3 pi

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Question 96 Chemical Bonding

NH₃ and NF₃ are both pyramidal. Why does NH₃ have a much larger dipole moment than NF₃?

Correct answer D. In NH₃ the lone pair moment adds to the bond moments, while in NF₃ it opposes them

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Question 97 Chemical Bonding

Which molecule is polar?

Correct answer D. CHCl₃

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Question 98 Chemical Bonding

Charges of ±1.6 × 10⁻¹⁹ C are separated by 1.0 × 10⁻¹⁰ m. What is the dipole moment (1 D = 3.34 × 10⁻³⁰ C m)?

Correct answer D. 4.8 D

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Question 99 Chemical Bonding

Why is the H–F bond much stronger than the H–I bond?

Correct answer C. H–F is shorter and more polar, so the attraction between atoms is greater

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Question 100 s- and p-Block Elements

Moving from sodium to chlorine across Period 3, the atomic radius generally ____.

Correct answer C. decreases

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