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Chemistry Assertion (A) & Reason (B) MCQ

Organic Chemistry: Some Basic Principles and Techniques · Gujarat Board (GSEB) STD 11 Science (GSEB - English Medium). 7 questions.

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Assertion (A) & Reason (B) MCQ

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7 questions · auto-graded multiple-choice test.

MCQ 11 Mark
Note : In the following questions a statement of Assertion $(A)$ followed by a statement of Reason $(R)$ is given. Choose the correct option out of the choices given below each question.
Assertion $(A)$ : Sulphur present in an organic compound can be estimated quantitatively by Carius method.
Reason $(R)$ : Sulphur is separated easily from other atoms in the molecule and gets precipitated as light yellow solid.
  • A
    Both $A$ and $R$ are correct and $R$ is the correct explanation of $A.$
  • B
    Both $A$ and $R$ are correct but $R$ is not the correct explanation of $A.$
  • ✓
    Both $A$ and $R$ are not correct.
  • D
    $A$ is not correct but $R$ is correct.
Answer
Correct option: C.
Both $A$ and $R$ are not correct.
Sulphur is estimated by Carius method in the form of white precipitate of $\mathrm{BaSO}_4$ on heating with fuming and $\mathrm{BaCl}_2$. If light yellow solid is obtained means impurities are present. It is filtered washed and then dried to get pure $\mathrm{BaSO}_4$.
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MCQ 21 Mark
Note : In the following questions a statement of Assertion $(A)$ followed by a statement of Reason $(R)$ is given. Choose the correct option out of the choices given below each question.
Assertion $(A)$ : All the carbon atoms in $\ce{H_2C = C = CH_2}$ are $sp^2$ hybridised
Reason $(R)$ : In this molecule all the carbon atoms are attached to each other by double bonds.
  • A
    Both $A$ and $R$ are correct and $R$ is the correct explanation of $A$.
  • B
    Both $A$ and $R$ are correct but $R$ is not the correct explanation of $A.$
  • C
    Both $A$ and $R$ are not correct.
  • ✓
    $A$ is not correct but $R$ is correct.
Answer
Correct option: D.
$A$ is not correct but $R$ is correct.
hybridization of $C$ can be find out by counting $\sigma$ bonds and $\pi$ bonds present on $C$ atom.
$_{3\sigma}\ \ \ \ \ \ \ \ \ \ _{2\sigma}\ \ \ \ \ \ _{3\sigma}$
$\text{CH}_2=\text{C}=\text{CH}_2$
$\ \ ^{1\pi}\ \ \ \ \ \ \ \ ^{1\pi} \ \ \ \ \ \ ^{1\pi}$
If $C$ has $3\sigma$ bounds, it is $\text{sp}^2$ hybridized. if $C $ has $2\sigma$ bound, it is sp hybridized.
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MCQ 31 Mark
Note : In the following questions a statement of Assertion $(A)$ followed by a statement of Reason $(R)$ is given. Choose the correct option out of the choices given below each question.
Assertion $(A)$ : Simple distillation can help in separating a mixture of propan $-1-\text{ol}\ ($boiling point $97^\circ C)$ and propanone $($boiling point $56^\circ C).$
Reason $(R)$ : Liquids with a difference of more than $20^\circ C$ in their boiling points can be separated by simple distillation.
  • ✓
    $A$ and $R$ both are correct, and $R$ is the correct explanation of $A.$
  • B
    $A$ and $R$ both are correct, but $R$ is not the correct explanation of $A$.
  • C
    $A$ is true but $R$ is false.
  • D
    $A$ and $R$ both are false.
Answer
Correct option: A.
$A$ and $R$ both are correct, and $R$ is the correct explanation of $A.$
The liquids are having sufficient difference in their boiling points. Liquids having different boiling points vaporize at different temperatures. The vapours are cooled and the liquids so formed are collected separately.
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MCQ 41 Mark
Note : In the following questions a statement of Assertion $(A)$ followed by a statement of Reason $(R)$ is given. Choose the correct option out of the choices given below each question.
Assertion $(A)$ : Pent $- 1-$ ene and pent $- 2 -$ ene are position isomers.
Reason $(R)$ : Position isomers differ in the position of functional group or a substituent.
  • ✓
    $A$ and $R$ both are correct, and $R$ is the correct explanation of $A.$
  • B
    $A$ and $R$ both are correct, but $R$ is not the correct explanation of $A$.
  • C
    $A$ is true but $R$ is false.
  • D
    $A$ and $R$ both are false.
Answer
Correct option: A.
$A$ and $R$ both are correct, and $R$ is the correct explanation of $A.$
When two or more compounds differ in the position of substituent atom or functional group on the carbon skeleton, they are called position isomers and this phenomenon is termed as position isomerism. Pent $-2-$ ene and pent $-l-$ ene are position isomers because differ in the position of double bond.
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MCQ 51 Mark
In the following Questions, the Assertion and Reason hrve been put forfiird. Read the statements csrefully end choose the correct alternative from the following:
Assertion : A Mixture of $o-$ nitrophenol and $p-$ nitrophenol can be separated by steam distillation.
Reason : $p-$ nitrophenol is steam volatile while $o-$ nitrophenol is not steam volatile.
  • A
    Both Assertion and Reason are true and Reason is the correct explanation of Assertion.
  • B
    Both Assertion rnd Reason are true but Reason is not the correct explenatlon of Assertion.
  • ✓
    Assertion is true but Reason is false.
  • D
    Both Assertion and Reason arc false.
Answer
Correct option: C.
Assertion is true but Reason is false.
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MCQ 61 Mark
Note : In the following questions a statement of Assertion $(A)$ followed by a statement of Reason $(R)$ is given. Choose the correct option out of the choices given below each question.
Assertion $(A)$ : Energy of resonance hybrid is equal to the average of energies of all canonical forms.
Reason $(R)$ : Resonance hybrid cannot be presented by a single structure.
  • A
    $A$ and $R$ both are correct, and $R$ is the correct explanation of $A.$
  • B
    $A$ and $R$ both are correct, but $R$ is not the correct explanation of $A$.
  • C
    $A$ is true but $R$ is false.
  • ✓
    $A$ and $R$ both are false.
Answer
Correct option: D.
$A$ and $R$ both are false.
Canonical structures always have more energy than resonance hybrid. Resonance hybrids are always more stable than any of the canonical structures. The delocalization of electrons lowers the orbitals energy and gives stability.
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MCQ 71 Mark
Note : In the following questions a statement of Assertion $(A)$ followed by a statement of Reason $(R)$ is given. Choose the correct option out of the choices given below each question.
Assertion $(A)$ : Components of a mixture of red and blue inks can be separated by distributing the components between stationary and mobile phases in paper chromatography.
Reason $(R)$ : The coloured components of inks migrate at different rates because paper selectively retains different components according to the difference in their partition between the two phases.
  • ✓
    $A$ and $R$ both are correct, and $R$ is the correct explanation of $A.$
  • B
    $A$ and $R$ both are correct, but $R$ is not the correct explanation of $A$.
  • C
    $A$ is true but $R$ is false.
  • D
    $A$ and $R$ both are false.
Answer
Correct option: A.
$A$ and $R$ both are correct, and $R$ is the correct explanation of $A.$
In paper chromatography, a special quality paper known as chromatography paper, is used. Chromatography paper contains water trapped in it, which acts as the stationary phase. A strip of chromatography paper spotted at the base with the solution of the mixture is suspended in a suitable solvent or a mixture of solvents. This solvent acts as the mobile phase. The solvent rises up the paper by capillary action and flows over the spot. The paper selectively retains different components according to their differing partition in the two phases. The paper strip so developed is known as a chromatogram. The spots of the separated coloured compounds are visible at different heights from the position of initial spot on the chromatogram.
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