With which one of the following elements silicon should be doped so as to give p-type of semiconductor ?

Germanium
Arsenic
Selenium
Boron

Solution

The semiconductors formed by the introduction of impurity atoms containing one electron less than the parent atoms of insulators are termed as p-type semiconductors. Therefore silicon containing 14 electrons is to be doped with boron containing 13 electrons to give a p-type semi-conductor.

Some of the properties of the two species, \(NO_{3}^{-}\) and H₃O⁺ are described below. Which one of them is correct?

Similar in hybridization for the central atom with different structures.
Dissimilar in hybridization for the central atom with different structures.
Isostructural with same hybridization for the central atom.
Isostructural with different hybridization for the central atom.

Solution

In \(NO_{3}^{-}\), nitrogen have sp² hybridisation, thus planar in shape. In H₃O⁺, oxygen is in sp³ hybridisation,thus tetrahedral geometry is expected but due to presence of one lp of electrons on central oxygen atom it is pyramidal in shape.

When alcohol reacts with concentrated H₂SO₄, intermediate compound formed is :

carbonium ion
alkoxy ion
alkyl hydrogen sulphate
none of the above

Solution

Reducing the pressure from 1.0 atm to 0.5 atm would change the number of molecules in one mole of ammonia to

25% of its initial value
50% of its initial value
75% of its initial value
None of the above

Solution

One mole of a substance contains the number of molecules which is independent of pressure.

Which among the following plots are linear (a – x) is the concentration of reactant remaining after time, t
(1)(a – x) vs t, for a first order reaction
(2)(a – x) vs t, for a zero order reaction
(3)(a – x) vs t, for a second order reaction
(4)1/(a – x) vs t, for a second order reaction

1 and 2
1 and 3
2 and 3
2 and 4

The acid which has a peroxy linkage is

sulphurous acid
pyrosulphuric acid
dithionic acid
caro’s acid

Solution

Caro’s acid is H₂SO₅ which contains one S – O –OH peroxy linkage. It is also known as permonosulphuric acid.

Chlorobenzene gives aniline with :

NH₃ + Cu₂O
NH₃ + H₂SO₄
NaNH₂
None of these

Solution

When alumina is heated with carbon in the atmosphere of nitrogen then products formed are

Al + CO
Al + CO + N₂
Al + CO₂
AlN +CO

Solution

In a Bohr model of an atom, when an electron jumps from n = 3 to n = 1, how much energy will be emitted?

2.15 × 10^–11 ergs
2.389× 10^–12 ergs
0.239 × 10^–10 ergs
0.1936 × 10^–10 ergs

Following are the molecules or ions of the type AH₃ where A is the central atom. In which of them does the central atom A use its sp² hybrid orbitals to form A-H bonds ?

PH₃
NH₃
CH₃⁺
CH₃^-

Solution

CH³⁺ has sp² hybridization because S orbital has one electron and p orbitals of central atom C have only two electrons. Therefore s and 2p orbitals participate in hybridization.

If sand S are respectively solubility and solubility product of a sparingly soluble binary electrolyte then :

s = S
s = S²
s = S^1/2
s = ¹/₂S

Solution

Which of the following statement is correct with respect to the property of elements with an increase in atomic number in the carbon family (group 14)?

atomic size decrease
ionization energy increase
metallic character decrease
stability of +2 oxidation state increase

Solution

In the carbon family the stability of +2 oxidation state increases with increase in atomic number due to inert pair effect.Therefore SnCl₄ is more stable than SnCl₂ & PbCl₂ is more stable than PbCl₄.

When CH₃Cl and AlCl₃ are used in Friedel-Crafts reaction,the electrophile is

Cl⁺
AlCl ₄^-
CH₃⁺
AlCl₂⁺

Solution

CH₃Cl + AlCl₃→CH₃⁺+AlCl₄^-

Here the electrophile is alkyl carbonium ion.

Which one of the following methods is neither meant for the synthesis nor for separation of amines?

Curtius reaction
Wurtz reaction
Hofmann method
Hinsberg method

Solution

Wurtz reaction is for the preparation of hydrocarbons from alkyl halide

RX + 2Na + XR → R - R + 2NaX

If 19 is the atomic number of an element, then this element will be

a metal with + 3 oxidation state
a metal with + 1 oxidation state
an inert gas
a metal with – 3 oxidation state

Solution

As atomic number, number 19 falls within group I of modern periodic table so it is an alkali metal with + 1 oxidation state.

DIRECTIONS: These are Assertion-Reason type questions. Question contains two statements:Statement-1 (Assertion) and Statement-2 (Reason). Answer these questions from the following four options.

Statement-1 :In crystal lattice, the size of the tetrahedral hole is larger than an octahedral hole.
Statement-2 :The cations occupy less space than anions in crystal packing.

Statement-1 is True, Statement-2 is True; Statement-2 is a correct explanation of Statement-1
Statement-1 is True, Statement-2 is True; Statement-2 is NOT a correct explanation of Statement-1
Statement-1 is True, Statement-2 is False
Statement-1 is False, Statement-2 is True

Solution

Tetrahedral holes are smaller in size than octahedral holes. Cations usually occupy less space than anions.

Solution

Solution

Which one is an example of multi molecular colloid system

Soap dispersed in water
Protein dispersed in water
Gold dispersed in water
Gum dispersed in water

Solution

Example of multi molecular colloid system is a gold dispersed in water.

In borax bead test which compound is formed?

Ortho-borate
Meta-borate
Double oxide
Tetra-borate

Solution

\(\underset{anhydrous}{Na_{2}B_{4}O_{7}}\overset{\Delta }{\rightarrow}\underset{sod.metaborate}{2NaBO_{2}}+\underset{Boric\: anhydride}{B_{2}O_{3}}\)

\(CuO+B_{2}O_{3}\rightarrow \underset{cupric\: meta\: borate(Bluebeed)}{Cu(BO_{2})_{2}}\)

UnAttempted

0

Attempted

0

Correct

0

Wrong