M.C.Q (1 Marks)

MCQ 11 Mark

Boiling point of alkanes are:

A
is independent of branching.
B
decreases with increase in molecular mass.
C
is independent of molecular mass.
✓
increases with increase in molecular mass.

Answer

Correct option: D.

increases with increase in molecular mass.

(d) increases with increase in molecular mass.
Explanation: As molecular mass increases, the magnitude of Van der Waals forces of attraction increases and hence boiling point increases accordingly.

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MCQ 21 Mark

Standard enthalpy of fusion or molar enthalpy of fusion is:

A
the enthalpy change that accompanies melting of one kg of a solid substance in the standard state.
B
the enthalpy change that accompanies vaporization of one kg of a solid substance in the standard state.
✓
the enthalpy change that accompanies melting of one mole of a solid substance in the standard state.
D
the enthalpy change that accompanies vaporization of one mole of a solid substance in the standard state.

Answer

Correct option: C.

the enthalpy change that accompanies melting of one mole of a solid substance in the standard state.

(c) the enthalpy change that accompanies melting of one mole of a solid substance in the standard state.
Explanation: Molar enthalpy of fusion (always increases i.e. $\Delta H =$ positive) is the amount of energy needed to change completely one mole of a substance from the solid phase to the liquid phase in the standard state.

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MCQ 31 Mark

Which one of the following is isoelectronic with Ne ?

A
$mg ^{2+}$
B
$Al ^{3+}$
C
$N ^{3-}$
✓
All of these

Answer

Correct option: D.

All of these

(d) All of these
Explanation: Isoelectronic species have same number of electrons.
$Ne ( Z =10)$ has 10 electrons.
$N ( Z =7)$ has 7 electrons and with addition of 3 more electrons it becomes $N ^{3-}$ anion which has 10 electrons.
$Mg ( Z =12)$ has 12 electron and with removal of 2 electrons it becomes $Mg ^{2+}$ cation which has 10 electrons.
$Al ( Z =13)$ has 13 electrons and with removal of 3 electrons it becomes $Al ^{3+}$ cation which has 10 electrons.
Since all the species have same number of electrons that is 10 , so they are isoelectronic.

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MCQ 41 Mark

Which conformation of ethane has the lowest potential energy?

A
Eclipsed
B
Skewed
✓
Staggered
D
All will have equal PE

Answer

Correct option: C.

Staggered

(c) Staggered
Explanation: In staggered conformation of ethane, any two H -atoms on adjacent C -atoms are as far apart as possible. As a result, the repulsions between the electron clouds of $\sigma$-bonds of two non bonded H -atoms are minimum and hence stability is maximum.

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MCQ 51 Mark

Write the state of hybridisation of carbon in $H _2 C = O$ and mention the molecular geometry also.

A
sp hybridised carbon, linear
✓
$sp ^2$ hybridised carbon, trigonal planar
C
$sp ^3$ hybridised carbon, tetrahedral
D
$sp ^3$ hybridised carbon, trigonal pyramidal

Answer

Correct option: B.

$sp ^2$ hybridised carbon, trigonal planar

(b) $sp ^2$ hybridised carbon, trigonal planar
Explanation: Due to the presence of a double bond in the carbonyl carbon ( $> C = O$ ), carbon is $sp ^2$ hybridised. This hybridization leads to a trigonal planar geometry which means a bond angle of $120^{\circ}$ around the C .

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MCQ 61 Mark

Which of the following are not redox reactions?
a) $K _4\left[ Fe ( CN )_6\right]+ H _2 SO _4+ H _2 O \rightarrow K _2 SO _4+ CO + FeSO _4+\left( NH _4\right)_2 SO _4$.
b) $CuSO _4+ NH _3 \rightarrow\left[ Cu \left( NH _3\right)_4 SO _4\right.$.
c) $M g+N_2 \rightarrow M g_3 N_2$
d) $I_2+3 Cl _2 \rightarrow 2 ICl _3$

A
c, d
B
b, d
C
b only
✓
a, b

Answer

Correct option: D.

a, b

(d) a, b
Explanation:
a) $K _4\left[ Fe ( CN )_6\right]+ H _2 SO _4+ H _2 O \rightarrow K _2 SO _4+ CO + FeSO _4+\left( NH _4\right)_2 SO _4$
b) $CuSO _4+ NH _3 \rightarrow\left[ Cu \left( NH _3\right)_4 SO _4\right.$
Since, oxidation number of each element does not change in these reactions, so these are not redox reactions.

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MCQ 71 Mark

Chlorine's $( Cl )$ relative atomic mass is 35.5 . this half number is due to

A
a half neutron
B
a half proton
✓
isotopes
D
a half electron

Answer

Correct option: C.

isotopes

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MCQ 81 Mark

The enthalpy of combustion of methane, graphite and dihydrogen at 298 K are, $-890.3 kJ mol ^{-1},-393.5 kJ mol ^{-1}$ and $-285.8 kJ mol ^{-1}$ respectively. Enthalpy of formation of $CH _4(g)$ will be

A
$+74.8 kJ mol ^{-1}$
B
$+52.26 kJ mol ^{-1}$
C
$-74.8 kJ mol ^{-1}$
D
$-52.27 kJ mol ^{-1}$

Answer

$\begin{aligned} & \text { (c) }-74.8 kJ mol ^{-1} \\ & \text { Explanation: } CH _4+2 O _2 \rightarrow CO _2+2 H _2 O \Delta H _1=-890.3 KJ / mol \ldots(1) \\ & C ( s )+ O _2 \rightarrow CO _2 \Delta H _2=-393.5 KJ / mol \ldots(2) \\ & H _2+0.5 O _2 \rightarrow H _2 O \Delta H _3=-285.8 KJ / mol \ldots(3) \\ & C ( s )+2 H _2 \rightarrow CH _4 \Delta H =\Delta H _2+2\left(\Delta H _3\right)-\Delta H _1 \\ & \Delta H =-393.5+2(-285.8)-(-890.3) \\ & =-74.8 kJ / mol \end{aligned}$

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MCQ 91 Mark

Number of angular nodes for 4d orbital is _________ .

✓
2
B
1
C
3
D
4

Answer

Correct option: A.

(a) 2
Explanation: Explanation: number of angular node=1 for 4d orbital, l=2

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MCQ 101 Mark

Maximum entropy will be in which of the following?

✓
water vapour
B
snow
C
liquid water
D
Ice

Answer

Correct option: A.

water vapour

(a) water vapour
Explanation: water vapour

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MCQ 111 Mark

Pairing of electrons in the orbitals belonging to the same subshell ( $p, d$ or f ) does not take place until each orbital belonging to that subshell is singly occupied. This is called

A
Pauli's exclusion principle
✓
Hund's rule of maximum multiplicity
C
Aufbau principle
D
None of these

Answer

Correct option: B.

Hund's rule of maximum multiplicity

(b) Hund's rule of maximum multiplicity
Explanation: Pairing of electrons in the orbitals belonging to the same subshell ( $p , d$ or f ) does not take place until each orbital belonging to that subshell has got one electron each, i.e. it is singly occupied. This is called Hund's rule of maximum multiplicity.

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MCQ 121 Mark

The number of moles of solute present in 1 kg of solvent is called:

A
molarity
B
normality
C
mole fraction
✓
molality

Answer

Correct option: D.

molality

(d) molality
Explanation: Mathematically, molality is expressed as, $\operatorname{Molality}(m)=\frac{\text { No. of moles of solute }}{\text { Mass of solvent in } kg }$

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Chemistry M.C.Q (1 Marks)

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