Chemistry Test 288

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Chemistry Test 288

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Weekly Quiz Competition

Question 1
4 / -1

The RMS speed of the molecule of diatomic gas is U.

The new RMS speed of the atom when the temperature is doubled and the molecule dissociates into two atoms.

A

B
U

C
2U

D
4U

Solution
Question 2
4 / -1

Which one of the following reaction yield a secondary amine :

A
Hoffmann bromamide reaction

B
Gabriel phthalimide reaction

C
Reduction of alkanamide with LiAlH₄

D
Reduction of alkylisocyanide with LiAlH₄

Solution
Question 3
4 / -1

Among the following, which is the strongest acid?

A
CH(CN)₃

B
CHI₃

C
CHBr₃

D
CHCl₃

Solution
Question 4
4 / -1

What quantity of electricity (in coulombs) is required to deposit 1 mole of Aluminium (Al) using electrolysis?

A
96500 C

B
193000 C

C
289500 C

D
386000 C

Solution
Question 5
4 / -1

A
−266

B
266

C
313

D
-313

Solution
Question 6
4 / -1

Reduction of > C = O to CH₂ can be carried out with

A
Catalytic reduction

B
Na/C₂H₅OH

C
Wolf-Kishner reduction

D
LiAlH₄

Solution

Step 1: Understanding the Wolff-Kishner reduction

The Wolff-Kishner reduction is a chemical reaction used to convert a carbonyl group (>C=O) into a methylene group (CH₂). It is particularly useful for reducing aldehydes and ketones to alkanes.

Step 2: Comparing with other reduction methods

Catalytic reduction (e.g., with H₂/Ni,Pt, or Pd) typically reduces a carbonyl group in an aldehyde or ketone to a hydroxyl group (−OH), forming an alcohol.

Na/C₂H₅OH (sodium in ethanol) is a reducing agent (Bouveault-Blanc reduction) used to reduce esters to primary alcohols, but not typically for the direct reduction of a ketone/aldehyde to an alkane.

LiAlH₄ (lithium aluminum hydride) is a strong reducing agent that reduces carbonyl groups in aldehydes, ketones, esters, and carboxylic acids to alcohols, but not to alkanes.
Question 7
4 / -1

Which of the following will not undergo aldol condensation

A
Acetaldehyde

B
Propanaldehyde

C
Benzaldehyde

D
Trideuteroacetaldehyde

Solution

Benzaldehyde will not undergo aldol condensation since it has no α-hydrogen.
Question 8
4 / -1

Phthalic acid reacts with resorcinol in the presence of concentrated H₂SO₄ to give:

A
Phenolphthalein

B
Alizarin

C
Coumarin

D
Fluorescein

Solution

The reaction between phthalic acid (or more commonly, phthalic anhydride) and resorcinol in the presence of concentrated sulfuric acid is a condensation reaction that produces fluorescein.
Question 9
4 / -1

Mixing of non-reacting gases is generally accompanied by

A
Decrease in entropy

B
Increase in entropy

C
Change in enthalpy

D
Change in free energy

Solution

Mixing of non-reacting gases is a spontaneous process because it increases the overall randomness or disorder of the system. Entropy is a thermodynamic property that measures this disorder. When different gases mix, the number of possible positions for each gas molecule increases, leading to a higher degree of randomness and thus an increase in entropy ( ΔS > 0 ).
Question 10
4 / -1

One mole of an ideal gas at 300 K is expanded isothermally from an initial volume of 1 litre to 10 litres. The change in internal energy for this process is (R = 2 cal mol⁻¹K⁻¹)

A
163.7 cal

B
850.2 cal

C
1381.1 cal

D
Zero

Solution

For an ideal gas, the internal energy (and energy) depends solely on its temperature. The formula for the change in internal energy ( ΔU ) is given by ΔU = nC_vΔT, where n is the number of moles, C_v is the molar heat capacity at constant volume, and ΔT is the change in temperature.

In an isothermal process, the temperature ( T ) remains constant, which means the change in temperature (ΔT) is zero. Substituting ΔT = 0 into the equation gives ΔU = nC_v× 0 = 0