Chemistry Test 215

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Chemistry Test 215

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Weekly Quiz Competition

Question 1
4 / -1

When one mole of monoatomic ideal gas at T K undergoes adiabatic change under a constant external pressure of 1 atm and changes volume from 1 litre to 2 litre, the final temperature (in Kelvin) would be

A

B

C
T

D

Solution
Question 2
4 / -1

Among the given anions, the strongest Bronsted base is

A
CIO^–

B
CIO₂^–

C
CIO₃^–

D
CIO₄^–

Solution

The strongest conjugated base has the weakest conjugate acid.

The order of acidic strength of oxoacids is HClO < />₂ < />₃ < />₄.

This can be explained by the order of oxidation states of chlorine atom in the oxoacids.

The order of the basic strength of the oxo anions is
Question 3
4 / -1

The pair of compounds which cannot exist together in solution is

A
NaHCO₃ and NaOH

B
Na₂CO₃ and NaHCO₃

C
Na₂CO₃ and NaOH

D
NaHCO₃ and NaCl

Solution

NaHCO₃ is an acid salt of H₂CO₃. It reacts with NaOH to yield Na₂CO₃ and H₂O.

NaHCO₃ + NaOH → Na₂CO₃ + H₂O
Question 4
4 / -1

Among KO₂, AlO₂^-, BaO₂ and NO₂⁺, which of the following contain(s) an unpaired electron?

A
NO₂⁺ and BaO₂

B
KO₂ and AlO₂^-

C
KO₂ only

D
BaO₂ only

Solution

Super oxide ion is paramagnetic due to an unpaired electron.

In KO₂, we have O₂^- ion, which has one unpaired electron.
Question 5
4 / -1

H₃BO₃ is

A
monobasic and a weak Lewis acid

B
monobasic and a weak Bronsted acid

C
monobasic and a strong Lewis acid

D
tribasic and a weak Bronsted acid

Solution

In boric acid (H₃BO₃), the boron atom has only six electrons and so, it is electron deficient i.e. it is a Lewis acid with one p-orbital vacant in its valence shell, which has no d-orbitals. Thus, it can accommodate only one electron pair in its outermost shell.

Hence, it is a Lewis acid and is monobasic.
Question 6
4 / -1

The number of P-O-P bridges in the structures of phosphorus pentoxide and phosphorus trioxide is

A
6, 6

B
5, 5

C
5, 6

D
6, 5

Solution

The structures of P₄O₁₀ and P₄O₆ are as follows.

Hence, the number of P-O-P bridges is 6 in each.
Question 7
4 / -1

A solution of (-)- 1 - chloro - 1 - phenylethane in toluene racemises slowly, in the presence of a small amount of SbCI₅, due to the formation of

A
free radical

B
carbanion

C
carbene

D
carbocation

Solution

In the presence of a small amount of SbCI₅, (-)- 1 - chloro - 1 - phenylethane forms a carbocation intermediate.

Being a planar species, a carbocation intermediate will lead to 50% retention of configuration and 50% inversion of configuration. Hence, it causes racemisation.
Question 8
4 / -1

How is the product formed in the below reaction?

A
Michael addition followed by aldol condensation

B
Aldol condensation followed by Michael addition

C
Mannich reaction

D
Knoevenagel reaction followed by aldol condensation

Solution
Question 9
4 / -1

Consider the following:

The above given sequence of reactions of A gives

A

B

C

D

Solution

The first step is Hoffmann-bromamide degradation and the second step is intramolecular nucleophilic aminolysis of ester.
Question 10
4 / -1

Which of the following surfactants will form micelles in aqueous solution at the lowest molar concentration under ambient conditions?

A
CH₃(CH₂)15N⁺(CH₃)₃Br^-

B
CH₃(CH₂)₁₁OSO₃-Na⁺

C
CH₃(CH₂)₆COO-Na⁺

D
CH₃(CH₂)₁₁N⁺(CH₃)₃Br^-

Solution

Options (a) and (b) are capable of forming micelles.

(1) CH₃(CH₂)₁₅N⁺(CH₃)₃Br^-

Cetyl trimethyl ammonium bromide

(2) CH₃(CH₂)₁₁OSO₃^-Na⁺

Sodium lauryl sulphate

But, critical concentration for micelle formation decreases as the molecular weight of hydrocarbon chain of surfactant grows because in this true solubility diminishes and the tendency of surfactant molecule to undergo association increases. So, option (a) is correct.