Chemistry Test

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Chemistry Test - 32

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Weekly Quiz Competition

Question 1
5 / -1

The decomposition of NH₃ on platinum surface is zero order reaction. If k = 2.5 × 10^-4 mol L^-1s^-1 the rate of production of H₂ is

A
2.5 × 10^-4 mol L^-1s^-1

B
7.5 × 10^-4 mol L^-1s^-1

C
5.0 × 10^-4 mol L^-1s^-1

D
10.0 × 10^-4 mol ^L-1s^-1

Solution
Question 2
5 / -1

What is the molecularity of the following elementary reaction: 2NO+O₂→2NO₂?

A
Zero

B
Three

C
Two

D
One

Solution

The molecularity of an elementary reaction is the number of reactant molecules involved in the rate-determining step. In the reaction 2NO+O₂→2NO₂ , two molecules of NO and one molecule of O₂(total of three molecules) participate in the elementary step. Thus, the molecularity is three.
Question 3
5 / -1

Which one of the following is an emulsion?

A
Smoke

B
Hair cream

C
Paint

D
Cheese

Solution

An emulsion is a type of colloid in which one liquid is dispersed in another immiscible liquid in the form of small droplets.

Hair cream is an example of an emulsion where oil droplets are dispersed in water. Paint can also be classified as an emulsion or a suspension depending on the type of paint.

Cheese, on the other hand, is a type of colloid where solid particles are dispersed in a liquid. Smoke is an aerosol, which is a type of colloid where solid or liquid particles are suspended in a gas.
Question 4
5 / -1

Which one of the following is NOT an example of colloids?

A
Milk

B
Jelly

C
Tincture of iodine

D
Fog

Solution

Tincture of iodine is NOT a colloid. A colloid is a mixture where particles (1–1000 nm) are dispersed in a medium and scatter light. Milk (emulsion), jelly (gel), and fog (aerosol) are colloids. Tincture of iodine is a true solution of iodine in alcohol, with molecular-sized particles that do not scatter light. Colloids can be separated by centrifugation (e.g., fat from milk), but true solutions cannot.
Question 5
5 / -1

Tyndall effect is not observed in which of the following --

A
Starch solution

B
Emulsions

C
Milk

D
Sugar solution

Solution

The Tyndall effect is the scattering of light as a light beam passes through a colloid. This effect is used to determine whether a mixture is a true solution or a colloid. Milk, starch solution and emulsions show Tyndall effect whereas sugar solution doesn’t show Tyndall effect.
Question 6
5 / -1

Directions For Questions

Directions: Read the following passage carefully:

A tertiary alcohol H upon acid-catalyzed dehydration gives a product I. Ozonolysis of I leads to compounds J and K. Compound J upon reaction with KOH gives benzyl alcohol and a compound L, whereas K on reaction with KOH gives only M.

...view full instructions

Which of the following statements is correct for compound (K)?

A
It reacts with alkaline KMnO₄ followed by acidic hydrolysis and forms benzoic acid.

B
It does not reacts with iodine and NaOH to form triiodomethane.

C
It is prepared by the reaction of benzene with benzoyl chloride in presence of anhydrous aluminium chloride.

D
It reacts with freshly prepared ammoniacal silver nitrate solution.

Solution

Assume K = PhCOCH₃ (acetophenone, based on aldol condensation).

Option A:

Alkaline potassium permanganate (KMnO₄) is a strong oxidizing agent. It can oxidize ketones under strong conditions by breaking the carbon chain next to the carbonyl group.

For the compound PhCOCH₃ (acetophenone), oxidation with alkaline KMnO₄ followed by acidification (H⁺) gives benzoic acid (PhCOOH) and small fragments.

So, this is correct because the methyl group attached to the carbonyl gets oxidized to form benzoic acid.

Option B:

The iodoform test detects methyl ketones (a CH₃ group attached to a carbonyl group) or compounds that can be oxidized to methyl ketones.

PhCOCH₃ is a methyl ketone, so it gives a positive iodoform test and forms a yellow precipitate of iodoform (CHI₃).

This is incorrect.

Option C:

The reaction of benzene with benzoyl chloride in the presence of a Lewis acid (Friedel-Crafts acylation) gives benzophenone (PhCOPh), not acetophenone (PhCOCH₃).

So, this is incorrect.

Option D:

Tollens' test is used to detect aldehydes, not ketones. Since PhCOCH₃ is a ketone, it does not react with Tollens' reagent.

This is also incorrect.
Question 7
5 / -1

Directions For Questions

Directions: Read the following passage carefully:

A tertiary alcohol H upon acid-catalyzed dehydration gives a product I. Ozonolysis of I leads to compounds J and K. Compound J upon reaction with KOH gives benzyl alcohol and a compound L, whereas K on reaction with KOH gives only M.

...view full instructions

Compound H is formed by the reaction of

A

B

C

D

Solution
Question 8
5 / -1

Directions For Questions

Directions: Read the following passage carefully:

A tertiary alcohol H upon acid-catalyzed dehydration gives a product I. Ozonolysis of I leads to compounds J and K. Compound J upon reaction with KOH gives benzyl alcohol and a compound L, whereas K on reaction with KOH gives only M.

...view full instructions

The structure of the compound I is

A

B

C

D

Solution

Compound "I" is formed when compounds J and K compound reacts with each other.
Question 9
5 / -1

Directions For Questions

Directions: Read the following passage carefully:

A tertiary alcohol H upon acid-catalyzed dehydration gives a product I. Ozonolysis of I leads to compounds J and K. Compound J upon reaction with KOH gives benzyl alcohol and a compound L, whereas K on reaction with KOH gives only M.

...view full instructions

When (J) is treated with acetic anhydride, in the presence of the corresponding salt of an acid, the product obtained is

A
cinnamic acid

B
crotonic acid

C
maleic acid

D
benzylic acid

Solution
Question 10
5 / -1

Directions For Questions

Directions: Read the following passage carefully:

A tertiary alcohol H upon acid-catalyzed dehydration gives a product I. Ozonolysis of I leads to compounds J and K. Compound J upon reaction with KOH gives benzyl alcohol and a compound L, whereas K on reaction with KOH gives only M.

...view full instructions

The structure of compounds J, K, and L, respectively, are

A
PhCOCH₃, PhCH₂COCH₃, and PhCH₂OO^-K ⁺

B
PhCHO, PhCH₂CHO and PhCOO^-K ⁺

C
PhCOCH₃, PhCH₂CHO, and CH₃COO^-K ⁺

D
PhCHO, PhCOCH₃, and PhCOO^-K ⁺

Solution