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Chemistry Assertion (A) & Reason (B) MCQ

Thermodynamics · UP Board (UPMSP) STD 11 Science (UPMSP - English Medium). 3 questions.

Questions

Assertion (A) & Reason (B) MCQ

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3 questions · auto-graded multiple-choice test.

MCQ 11 Mark
Notes : 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 $(A)$ : Combustion of all organic compounds is an exothermic reaction.
Reason $(R)$ : The enthalpies of all elements in their standard state are zero.
  • A
    $A$ and $R$ both are correct, and $R$ is the correct explanation of $A.$
  • ✓
    $A$ 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: B.
$A$ and $R$ both are correct, but $R$ is not the correct explanation of $A$.
Combustion of organic compounds is always exothermic. Heat or enthalpy of formation of natural elements in their standard state is considered to be zero.
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MCQ 21 Mark
Notes : 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 $(A)$ : A liquid crystallises into a solid and is accompanied by decrease in entropy.
Reason $(R)$ : In crystals, molecules organise in an ordered manner.
  • ✓
    $A$ 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 a liquid crystallizes, its entropy decrease.
Since in crystaline form, the molecules are more ordered.
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MCQ 31 Mark
Notes : 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 $(A)$ : Spontaneous process is an irreversible process and may be reversed by some external agency.
Reason $(R)$ : Decrease in enthalpy is a contributory factor for spontaneity.
  • A
    $A$ and $R$ both are correct, and $R$ is the correct explanation of $A.$
  • ✓
    $A$ 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: B.
$A$ and $R$ both are correct, but $R$ is not the correct explanation of $A$.
For spontaneus process, energy factor should be favourable means $\Delta\text{H}=-\text{ve}$ and randomness should be positive.
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