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Chemistry M.C.Q (1 Marks)

Model Paper 10 · Rajasthan Board (RBSE) STD 11 Science (Rajasthan - English Medium). 12 questions.

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M.C.Q (1 Marks)

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12 questions · 11 auto-graded MCQ + 1 self-marked written.

MCQ 11 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 21 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 31 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 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 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 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
(c) isotopes
Explanation: isotopes
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MCQ 81 Mark
Number of angular nodes for 4d orbital is _________ .
  • ✓
    2
  • B
    1
  • C
    3
  • D
    4
Answer
Correct option: A.
2
(a) 2
Explanation: Explanation: number of angular node=1 for 4d orbital, l=2
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MCQ 91 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 101 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 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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