All Free Chemistry MCQs with Answers

• A. The presence of halogen atom
• B. The polarity of C - Mg bond
• C. The presence of Mg atom
• D. The polarity of C - X bond

Explanation: Grignard reagents are reactive due to the polarity of the carbon-magnesium (C-Mg) bond.

• A. Two step reactions
• B. Multistep reactions
• C. Single step reactions
• D. None of these

Explanation: SN2 reactions are single step reactions. The correct answer is C. In SN2 (substitution nucleophilic bimolecular) reactions, the…

• A. E1, S2
• B. E2, S1
• C. E2, S2
• D. E1, S1

Explanation: The correct answer is d) E1, S1. The first step of both E1 and S1 reactions involves the formation of a carbocation intermediate.

• A. From the side of leaving group
• B. Opposite to the leaving group
• C. In front of the leaving group
• D. Below the leaving group

Explanation: In an SN2 (substitution nucleophilic bimolecular) reaction, the nucleophile attacks the electrophilic carbon from the opposite side of the…

• A. Ca in anhydrous ether
• B. Mg in dry ether
• C. Mg in moist ether
• D. Ca in dry ether

Explanation: Grignard reagents are produced by the reaction of alkyl halides with magnesium (Mg) in dry ether. The correct option is B.

• A. Multistep reaction
• B. Two step reaction
• C. Concerted reaction
• D. Three step reaction

Explanation: SN1 reactions are two-step reactions. The correct answer is B. In the first step, the leaving group departs, forming a carbocation…

• A. Electrophilic carbon
• B. Nucleophilic carbon
• C. β-hydrogen
• D. None of these

Explanation: In a reaction involving both alkyl halide and a base, the base will attack on β-hydrogen.

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

Explanation: Option c is correct. In SN1 reactions, since the nucleophile attacks the planar carbocation intermediate, it can indeed approach from…

• A. Electrophile
• B. Lewis acid
• C. Electron deficient species
• D. Bear all properties

Explanation: The function of AlCl3(anhydrous), in the Friedel-Craft reaction, is to produce electrophile, which later adds to the benzene nucleus.

• A. My brother, you and myself did it
• B. You, my brother and myself did it.
• C. My brother, you and me did it.
• D. You, my brother, and I did it.

Explanation: The correct sentence is (D) "You, my brother, and I did it." It uses the correct subject pronouns "you" and "I," and correctly places "my…

• A. Each of the chemical antiseptics was more harmfully to the leucocytes than to the germs.
• B. Each of the chemical antiseptics was more harmful to the leucocytes then to the germs.
• C. Each of the chemical antiseptics were more harmful to the leucocytes than to the germs.
• D. Each of the chemical antiseptics was more harmful to the leucocytes than to the germs.

Explanation: Each of the chemical antiseptics was more harmful to the leucocytes than to the germs.

• A. Electrons
• B. Protons
• C. Alpha particles
• D. Neutrons

Explanation: α-particles consist of 2 protons and 2 neutrons, which have 4 times higher mass than neutrons, and thus low penetration power.

• A. -4 C
• B. - 1 C
• C. 0 C
• D. 4 C

Explanation: As density is inversely proportional to the volume, the density of water increases when the temperature is lowered.

• A. Higher than water
• B. Lower than water
• C. Similar to water
• D. Higher than 1.59/cm3

Explanation: The density of ice is lower than water. The density of water is 1.000 g/cm3 at 0°C, while the density of ice is 0.917 g/cm3 at 0°C.

• A. 273K
• B. 373K
• C. 277K
• D. 509K

Explanation: This is equal to 4 degree celsius mentioned in punjab book page 87 under structure of ice.

• A. 0°C
• B. 2°C
• C. 4°C
• D. 100°C

Explanation: Water has its maximum density at 4°C because hydrogen bonding produces an open structure near freezing, while warming from 0°C to 4°C…

• A. spherical
• B. dumb-bell shaped
• C. double dumb-bell shaped
• D. irregular

Explanation: A p orbital has two lobes on either side of the nucleus with a node at the nucleus itself, giving the familiar dumb-bell shape.

• A. By burning of gas
• B. By the bombardment of cathode rays on gas molecules
• C. By cooling of the gas
• D. From the anode like cathode rays, produced from cathode

Explanation: Positive rays, also known as canal rays or anode rays, are produced by the bombardment of cathode rays on gas molecules.

• A. de-Broglie dual nature of matter
• B. Bohr's model
• C. Planck's Quantum theory
• D. Rutherford's atomic model

Explanation: The relationship between the energy (E) of a photon of light and its frequency (ν) is given by Planck's Quantum theory and is expressed by…

• A. Zeeman's effect
• B. Stark's effect
• C. Compton effect
• D. Photo electric effect

Explanation: The splitting of spectral lines when an atom is subjected to a magnetic field is known as the Zeeman effect.