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Chemistry M.C.Q (1 Marks)

Model Paper 3 · 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 · auto-graded multiple-choice test.

MCQ 11 Mark
In Ostwald's process for the manufacture of nitric acid, the first step involves the oxidation of ammonia gas by oxygen gas to give nitric oxide gas and steam. What is the maximum weight of nitric oxide that can be obtained starting only with 10.00 g of ammonia and 20.00 g of oxygen?
  • ✓
    15g of NO
  • B
    20g of NO
  • C
    16g of NO
  • D
    25g of NO
Answer
Correct option: A.
15g of NO
(a) 15 g of NO
Explanation: The reaction that takes place in ammonia and oxygen is given below:
$
\underset{68 g}{4 NH_3}+\underset{160 g}{5 O_2} \rightarrow \underset{120 g}{4 NO}+6 H_2 O
$
Limiting reagent
160 g of oxygen reacts with 68 g of ammonia
20 g of oxygen reacts with $\frac{68 \times 20}{160}=8.5 g$ of ammonia
Therefore for 20 g of oxygen 8.5 g of ammonia is used. Therefore 1.5 g ammonia is in excess and therefore oxygen is the limiting reagent.
$
160 g \text { of } O_2 \text { produces }=120 g \text { of } NO
$
Therefore, 20 g of $O _2$ produces $=\frac{120 \times 20}{60}=15 g$ of NO.
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MCQ 21 Mark
Enthalpies of formation of $CO ( g ), CO _2(g), N _2 O ( g )$, and $N _2 O _4(g)$ are $-110,-393,81$, and $9.7 kJ mol ^{-1}$ respectively. Find the value of $\Delta_{ r } H$ for the reaction: $N _2 O _4(g)+3 CO ( g ) \rightarrow N _2 O ( g )+3 CO _2(g)$
  • A
    $-850 kJ$
  • B
    $-600 kJ$
  • ✓
    $-778 Kj$
  • D
    $-802 kJ$
Answer
Correct option: C.
$-778 Kj$
(c) -778 kJ
Explanation: Heat of reaction, $\Delta_r H =\sum \triangle_r H_{\text {products }}-\sum \Delta_r H_{\text {reactants }}$
$
\begin{aligned}
& \Rightarrow \Delta_r H=\left[\Delta_f H\left(N_2 O\right)+3 \Delta_f H\left(CO_2\right)\right]-\left[\Delta_f H\left(N_2 O_4\right)+3 \Delta_f H(CO)\right] \\
& \left.\Rightarrow \Delta_r H=[81+\{3 \times(-393)\}]-99.7+\{3 \times(-110)\}\right] kJ \\
& \Rightarrow \Delta_r H=-777.7 kJ \approx-778 kJ
\end{aligned}
$
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MCQ 31 Mark
Which of these is not a characteristic of Aromatic Hydrocarbons?
  • A
    Carbon atoms form a closed chain or ring.
  • ✓
    Carbon atoms form a an open chain.
  • C
    They may contain double bonds.
  • D
    They are special type of cyclic compounds.
Answer
Correct option: B.
Carbon atoms form a an open chain.
(b) Carbon atoms form a an open chain.
Explanation: Aromatic hydrocarbon is not an open chain. They are ring structures. they contain one or more benzene rings either fused or isolated in their molecules.
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MCQ 41 Mark
Which of the following always has a negative value?
  • A
    Heat of reaction
  • B
    Heat of solution
  • C
    Heat of formation
  • ✓
    Heat of combustion
Answer
Correct option: D.
Heat of combustion
(d) Heat of combustion
Explanation: Combustion is an exothermic process. Hence heat of combustion has a negative value.
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MCQ 51 Mark
The effective distance between the centre of the nucleus of an ion and the point up to which the nucleus has an influence on its electron cloud is called _____________.
  • ✓
    ionic radius
  • B
    cationic radius
  • C
    covalent radius
  • D
    anionic radius
Answer
Correct option: A.
ionic radius
(a) ionic radius
Explanation: Since 'Ionic radius' is defined as the effective distance from the centre of the nucleus of an ion up to which it has an influence on its electron cloud. The correct answer is " ionic radius ".
The term Ionic radius is a general term used for both the cations as well as anions.
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MCQ 61 Mark
Give the number of electrons in the species, $O _2$ and $O _2{ }^{+}$.
  • A
    32 and 16
  • B
    16 and 14
  • C
    16 and 8
  • ✓
    16 and 15
Answer
Correct option: D.
16 and 15
(d) 16 and 15
Explanation: There are 8 protons in a single atom of oxygen and 8 neutrons. Thus, a molecule of oxygen $\left( O _2\right)$ would contain 16 of each. To gain + charge it must have to loose one electron. So number of electrons in $O_2^{+}=16-1=15$.
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MCQ 71 Mark
Which of the following is the correct IUPAC name of the given compound?
Image
  • A
    4, 4-Dimethyl-3-ethylheptane
  • B
    4, 4-Bis(methyl)-3-ethylheptane
  • ✓
    3-Ethyl-4, 4-dimethylheptane
  • D
    5-Ethyl-4, 4-dimethylheptane
Answer
Correct option: C.
3-Ethyl-4, 4-dimethylheptane
(c) 3-Ethyl-4, 4-dimethylheptane
Explanation: In IUPAC name, functional groups are written in alphabetical order. Locant 3 is assigned to ethyl group and the two methyl groups are present on C-4. The longest C chain has 7 C atoms so the IUPAC name is 3-ethyl-4,4-dimethylheptane.
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MCQ 81 Mark
Choose the correct answer. A thermodynamic state function is a quantity:
  • A
    used to determine pressure volume work.
  • B
    whose value depends on temperature only.
  • C
    used to determine heat changes.
  • ✓
    whose value is independent of path.
Answer
Correct option: D.
whose value is independent of path.
(d) whose value is independent of path.
Explanation: A state function value depends only on the state of the system and is independent of path.
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MCQ 91 Mark
Which one of the following depends upon variations in temperature?
  • ✓
    Both Normality and Molarity
  • B
    Normality
  • C
    Molarity
  • D
    Molality
Answer
Correct option: A.
Both Normality and Molarity
(a) Both Normality and Molarity
Explanation: Since Molarity and Normality both the modes of expression to represent the strength of a solution are volumedependent, a variation in temperature of the solution results in a change in concentration or strength of the solution. It is due to the thermal expansion of liquids.
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MCQ 101 Mark
According to quantum mechanics, $|\psi|^2$ (r) the wave function squared gives:
  • A
    probability of finding an electron
  • ✓
    probability density of finding an electron
  • C
    probability density of finding a proton
  • D
    probability of finding a neutron
Answer
Correct option: B.
probability density of finding an electron
(b) probability density of finding an electron
Explanation: The probability density of finding an electron at a point within an atom, predicts the region around the nucleus where the electron can most probably be found.
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MCQ 111 Mark
Acetylene is prepared by the action of water on:
  • A
    all of these
  • ✓
    $CaC _2$
  • C
    Silicon carbide
  • D
    $Al _4 C _3$
Answer
Correct option: B.
$CaC _2$
(b) $CaC _2$
Explanation: The reaction of $CaC _2$ (Calcium carbide) with water produces acetylene $\left( C _2 H _2\right)$.
The chemical equation for the reaction of calcium carbide $\left( CaC _2\right)$ with water to yield acetylene $(H C \equiv C H)$ is
$
CaC_2+H_2 O \rightarrow CaO+C_2 H_2
$
The calcium oxide $( CaO )$ is formed as a byproduct, which simultaneously reacts with water to give $Ca ( OH )_2$
$
CaO+H_2 O \rightarrow Ca(OH)_2
$
Thus, the overall reaction is,
$
CaC_2+2 H_2 O \rightarrow C_2 H_2+Ca(OH)_2
$
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MCQ 121 Mark
The electrons are ejected from the metal surface when the light of certain frequencies strikes the surface is called ____________________.
  • A
    Faraday’s cathode ray discharge model
  • B
    Thomson model for electron
  • ✓
    Photoelectric effect
  • D
    Planck's quantum theory
Answer
Correct option: C.
Photoelectric effect
(c) Photoelectric effect
Explanation: Electrons are ejected from the metal when the light of a certain frequency strikes the surface of a metal, This phenomenon is known as the photoelectric effect and the ejected electrons are called photoelectrons.
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