All Free Chemistry MCQs with Answers

• A. Carbanion
• B. Carbocation
• C. Carbene
• D. Alkoxide ion

Explanation: During the reduction of aldehydes with NaBH4, the "alkoxide ion" is seen as the intermediate formed hence the answer is D.

• A. Primary and secondary
• B. Secondary and tertiary
• C. Primary and tertiary
• D. Primary, secondary and tertiary

Explanation: a) Primary and secondary:This option suggests that both primary and secondary halogenoalkanes can react with alkali by an SN2…

• A. BF3
• B. SO3
• C. AlCl3
• D. CN

Explanation: Nucleophiles are elements/compounds containing extra pairs of electrons.

• A. A carbocation
• B. A free radical
• C. A carbanion
• D. An intermediate complex

Explanation: When nucleophilic substitution takes place bond between C and X dissociates.

• A. Substrate
• B. Nucleophile
• C. Both Options A and B are correct
• D. None of these options are correct

Explanation: In SN2 reactions, the rate of the reaction is directly proportional to the concentration of the nucleophile and the concentration of the…

• A. From the opposite side of the leaving group
• B. From the front of the leaving group
• C. From both sides
• D. None of these options are correct

Explanation: The correct answer is: From both sides. The nucleophile can attack the carbocation from either the front or the back side during an SN1…

• A. Water
• B. Benzene
• C. Carbon Tetrachloride
• D. Carbon disulphide

Explanation: SN1 reactions are favored by Polar prototic Solvents. These are polar solvents that are able to show hydrogen bonding.

• A. A carbocation
• B. A free radical
• C. A carbanion
• D. An intermediate complex

Explanation: In the first step of an SN1 reaction, the halide atom of the alkyl halide is removed, and the carbon atom becomes sp2 hybridized.

• A. Sp2 to sp3
• B. Sp to sp2
• C. Sp3 to sp2
• D. Sp to sp3

Explanation: Normally, a carbon atom is sp3 hybridized. In the transition state of the SN2 mechanism, the carbon atom is sp2 hybridized due to its…

• A. First
• B. Second
• C. Third
• D. Zero

Explanation: For a second-order reaction, the half-life is inversely proportional to the initial concentration of the reactant, Hence the correct…

• A. 10 s
• B. 20 s
• C. 40 s
• D. 400 s

Explanation: b) 20 s:This option suggests that the half-life of the reaction would remain the same at 20 s when the initial pressure of A is increased…

• A. Second order reaction
• B. Zero order reaction
• C. Pseudo - unimolecular reaction
• D. First order reaction

Explanation: A pseudo-unimolecular reaction or pseudo first order reaction s a reaction whose rate depends on the concentration of a single reactant…

• A. First order reaction
• B. Second order reaction
• C. Third order reaction
• D. Zero order reaction

Explanation: In the zero-order reaction, the rate is independent of the concentration of reactants and hence, the units of rate and rate constant…

• A. 2nd
• B. 3rd
• C. 1st
• D. Zero

Explanation: It is second order reaction. Ozone reacts readily with nitric oxide to yeild nitrogen dioxide and oxygen

• A. 1st order reaction
• B. 2nd order reaction
• C. Negative order of reaction
• D. Zero order of reaction

Explanation: The rate of reaction is inversely proportional to the concentration of the reactant in a second-order reaction (option b).

• A. a x b
• B. a - b
• C. b - a
• D. a + b

Explanation: The exponents a+b represents the order of reaction.

• A. Direction of reaction
• B. Extent of reaction
• C. Order of reaction
• D. Temperature of reaction

Explanation: Option C "Order of Reaction " is the correct answer. Order of reaction may be defined as the number of molecules or reactants…

• A. Second order
• B. Zero order
• C. First order
• D. Third order

Explanation: In a second-order reaction, the relationship between half-life and concentration is such that the half-life is inversely proportional to…

• A. Number of reactant molecules
• B. Number of moles of reactants
• C. Number of moles of products
• D. Order of Reactions

Explanation: The formula for the half-life of a reaction, t1/2 = 1 / [A(a(n-1))], includes the term (n-1), where n represents the order of the reaction.

• A. It's in excess
• B. It's a solvent
• C. It's a solute
• D. Both A and B

Explanation: A Pseudo first-order reaction can be defined as a second-order or bimolecular reaction that is made to behave like a first-order reaction.