Chemistry Test

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Chemistry Test - 31

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Weekly Quiz Competition

Question 1
1 / -0

The reaction between phosphorus (P₄ ) and hydrogen (H₂ ) can result in the formation of phosphine (PH₃ ) as shown :

\(\mathrm{P}_{4}(s)+6 H_{2}(g) 4 P H_{3}(g)\)

The graph shows the change in concentration of hydrogen for this reaction in which the system was disturbed after four hours.

Which of the following could explain the change in hydrogen concentration at time = 4 hours

A
The volume on the reaction vessel was decreased

B
A catalyst was added

C
The pressure on the reaction mixture was decreased

D
More phosphorus was added

Solution

Volume of vessel decreased, sudden increase in [H₂ ] and then again decreasing reaction moving in forwarding direction to achieve a state of new equilibrium.

A catalyst does not affect the concentration.

Increase in pressure would decrease concentration as reaction favoured forward

P₄(s) will have no effect on k_P and concentration of H₂(g)

( because active mass of solid is taken to be unit )

Factors Affecting Chemical Equilibrium /Le Chatelier's Principle

“Change in any of the factors that determine the equilibrium conditions of a system will shift the equilibrium in such a manner to reduce or to counteract the effect of the change.”
The principle is very helpful in predicting qualitatively the effect of change in concentration, pressure or temperature on a system in equilibrium.

Hence, the correct option is (A)
Question 2
1 / -0

When aniline is treated with fuming sulphuric acid followed by heating at temperature 475 K it gives :

A
Sulphanilic acid

B
Aniline sulphate

C
o-aminobenzene sulphonic acid

D
m-aminobenzene sulphonic acid

Solution

Examples on Sulphonation

Sulphonation: Sulphonation is carried out in the presence of sulphuric acid. The amino group in aniline is a basic group. Therefore, an acid-base reaction takes place to form anilinium hydrogensulphate salt. This salt undergoes rearrangement at a high temperature to give sulphanilic acid.

Hence, the correct option is (A)
Question 3
1 / -0

The structure of H₂O₂ is :

A
Spherical

B
Non - planar

C
Planar

D
Linear

Solution

In H₂O₂, the O - H groups are not in the same plane. So it has non - planar structure. If has a half - opened book structure in which the two O - H groups lie on the two pages of the book. The angle between two pages of the book is 94^o and H - O - O bond angle is 97^o.

Hydrogen peroxideis a chemical compound with the formula H₂O₂. In its pure form it is a colourless liquid, slightly more viscous than water; however, for safety reasons it is normally used as an aqueous solution. Hydrogen peroxide is the simplest peroxide (a compound with an oxygen-oxygen single bond) and finds use as a strong oxidizer, bleaching agent and disinfectant. Concentrated hydrogen peroxide, or 'high-test peroxide,' is a reactive oxygen species and has been used as a propellant in rocketry.

Hydrogen peroxide is often described as being “water but with one more oxygen atom”, a description which can give the incorrect impression that there is a great deal of similarity between the two compounds. Pure hydrogen peroxide will explode if heated to boiling, will cause serious contact burns to the skin and can set materials alight on contact. For these reasons it is usually handled as a dilute solution (household grades are typically 3-6%). Its chemistry is dominated by the nature of its unstable peroxide bond.

Hence, the correct option is (B)
Question 4
1 / -0

0.765 g acid gives 0.535g of CO₂ and 0.138 g of H₂O. What will be the ratio of percentage of carbon and hydrogen ?

A
19 : 2

B
20 : 1

C
15 : 2

D
10 : 1

Solution

\(\%\) of \(\mathrm{C}=\frac{12}{44} \times \frac{0.535}{0.765} \times 100=19.07 \%\)
\(\%\) of \(\mathrm{H}=\frac{2}{18} \times \frac{0.138}{0.765} \times 100=2.00 \%\)
Hence, \(\frac{\% \text { of carbon }}{\% \text { of hydrogen }}=\frac{19.07}{2.00} \approx 19: 2\)
Percentage composition Percentage composition of the compound is the relative mass of each of the constituent element in 100 parts of it. If the molecular mass of a compound is M and \(B\) is the mass of an element in the molecule, then
Percentage of element \(=\frac{\text { Mas of clement }}{\text { Molocular mass }} \times 100=\frac{\mathrm{x}}{\mathrm{M}} \times 100\)
Hence, the correct option is (A)
Question 5
1 / -0

Ethanol and methanol are miscible in water due to:

A
dissociation of water

B
their acidic character

C
allyl groups

D
hydrogen bonding

Solution

Being less bulky they can form hydrogen bond easily and are miscible with water.
Hence, the correct option is (D)
Question 6
1 / -0

Treatment of cyclopentanone with methyl lithium gives which of the following species?

A
Cyclopentanonyl radical

B
Cyclopentanonyl biradical

C
Cyclopentanonyl anion

D
Cyclopentanonyl cation

Solution

Treatment of cyclopentanone with methyllithium gives cyclopentanonyl anion.
Hence, the correct option is (C)
Question 7
1 / -0

\(C_{2} H_{5} O H \stackrel{C u / 300^{\circ} C}{\longrightarrow} X\)

In the above reaction, the molecular

formula of \(X\) is:

A
C₄H₆O

B
C₄H₁₀O

C
C₂H₄O

D
C₂H₆O

Solution

Ethanol vapours on being passed over heated \(C u\), it forms acetaldehyde. The reaction is:
\(C_{2} H_{5} O H \stackrel{C u / 300^{\circ} C}{\longrightarrow} C H_{3} C H O+H_{2}\)
Hence, the correct option is (C)
Question 8
1 / -0

Which of the following ether is called phenetole?

A
PhOCH₃

B
PhOC₂H₃

C
PhOC₃H₇

D
p−NO₂−C₆H₄OC₂H₅

Solution

PhOC₂H₃ is called phenetole.

Hence option B is correct.
Question 9
1 / -0

Which of the following given condensation with hydroxyl amine but does not undergo self condensation?

A
Methanal

B
Propanal

C
Acetone

D
Ethanal

Solution

Methanal
Or
Formaldehyde
Methanal or formaldehyde doess not contain an alpha H atom Hence, it gives condensation with hydroxyl amine but does not undergo self condensation.
Hence, the correct option is (A)
Question 10
1 / -0

An alcohol with D.U =1 exists having a 2° hydroxy group with the molecular formula of C₃H₆O is:

A
isopropanol

B
propenol

C
cyclopropenol

D
cyclopropanol

Solution

D.U =1

1 D.U. suggests unsaturated alcohol or cyclic 2°alcohol with three C atoms; 2°alcohol cannot be unsaturated, so it is cyclic.

Hence, option D is correct