Today's Test - Chemistry

The only non-metal which is liquid at ordinary temperature is

Hg
Br₂
NH₃
None of the above

Dipole moment of CO₂ is zero which implies that

Carbon and oxygen have equal electronegativities
Carbon has no polar bond
CO₂ is a linear molecule
Carbon has bond moments of zero value

Solution

O^?- = C^?+ = O^?- linear molecule hence ? = 0.

Furnaces are lined with calcium oxide because

it gives off oxygen on heating
it gives strong light on heating
it is refractory and basic
it is not affected by acids

The gas used in air ships is :

Solution

Hydrogen is lighter than helium but still helium is used in ballons because hydrogne is highly explosive and reactive gas. It may lead to accident.

Dipole moment of p-nitroaniline, when compared to nitrobenzene (X) and aniline (Y) will be :

smaller than both (X) and (Y)
greater than both (X) and (Y)
greater than (Y) but smaller than (X)
equal to zero

Solution

Group moment of –NO₂ is –3.98D(acting towards the benzene ring) and that of–NH₂ is + 1.5D(acting away from the group). Hence moments of both the groups in p-positions will act in the same direction.

An atom with high electronegativity has

large size
high ionisation potential
low electron affinity
low ionisation potential

Solution

An atom with high electronegativity has high IP.

When a strong beam of light is passed through a colloidal solution, the light will

be reflected
be scattered
be refracted
give a rainbow

Solution

It is due to Tyndall effect.

Solubilities of three sparingly soluble salts XY (K_sp), XY₂(K’_sp) and X₂Y₃(K”_sp) are equal in water. What will be the correct order of their solubility products –

K_sp < K'_sp < K''_sp
K_sp < K''_sp < K'_sp
K''_sp < K'_sp < K_sp
K''_sp < K_sp < K'_sp

Solution

Since for sparingly soluble salts, solubility (s) will be less than one. Therefore as the powers of s increases in K_sp expression, magnitude of K_sp will become smaller.

Which of the following exists as covalent crystals in the solid state ?

Iodine
Silicon
Sulphur
Phosphorus

Solution

Among the given crystals, only silicon exists as a covalent solid. It has diamond like structure.

Choose the amide which on reduction with LiAlH₄ yields a secondary amine

Ethanamide
N-Methylethanamide
N, N-dimethylethanamide
Phenylmethanamide

Solution

A compound contains 54.55 % carbon, 9.09% hydrogen ,36.36% oxygen. The empirical formula of this compound is :

C₃H₅O
C₄H₈O₂
C₂H₄O₂
C₂H₄O

Solution

Which of the following statements about H₃BO₃ is not correct?

It is a strong tribasic acid
It is prepared by acidifying an aqueous solution of borax
It has a layer structure in which planar BO₃ units are joined by hydrogen bonds
It does not act as proton donor but acts as a Lew is acid by accepting a lone pair of electrons

Solution

H₃BO₃ is a weak mono basic acid.

The pair of species with the same bond order is :

\(O_{2}^{2-}\),B₂
\(O_{2}^{+2}\), NO⁺
NO, CO
N₂, O₂

Solution

The rate of reaction is doubled for every 10°C rise in temperature. The increase in reaction rate as a result of temperature rise from 10°C to 100°C is

Solution

As the rate of reaction get doubled for every 10°C rise in temperature. Hence the increase in reaction rate as a result of temperature rise from 10°C to 100°C is equal to = 2⁹ = 512

In the diazotization of arylamines with sodium nitrite and hydrochloric acid, an excess of hydrochloric acid is used primarily to

Supress the concentration of free aniline available for coupling
Supress hydrolysis of phenol
Ensure a stoichiometric amount of nitrous acid
Neutralise the base liberated

Solution

Excess of HCl is used to convert free aniline to aniline hydrochloride otherwise free aniline would undergo coupling reaction with benzenediazonium chloride.

The shape of methyl carban ion is similar to that of –

BF₃
NH₃
methyl free radical
methyl carbocation

Solution

Methyl carbanion is sp³ hybridised, with three bond pairs and one lone pair same is the case with NH₃.

Activated charcoal is employed to remove colouring matter from pure substances. It works by :

Bleaching
Oxidation
Reduction
Adsorption

Solution

Activated charcoal is an allotropic form of carbon made by heating or chemically oxidizing sawdust or peat. It has large surface area and acts as adsorbant.

In India at the occasion of marriages, the fire works used give green flame. Which one of the following radicals maybe present?

Na⁺
K⁺
Ba²⁺
Ca²⁺

What is the product when acetylene reacts with hypochlorous acid?

CH₃COCl
ClCH₂CHO
Cl₂CHCHO
ClCHCOOH

Solution

Sewage water is purified by

aquatic plants
micro oganisms
light
fishes

Solution

Sewage water is purified by micro-organisms.