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Chemistry Assertion (A) & Reason (B) MCQ

Redox Reactions · Rajasthan Board (RBSE) STD 11 Science (Rajasthan - English Medium). 4 questions.

Questions

Assertion (A) & Reason (B) MCQ

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4 questions · self-marked practice — reveal the answer and mark yourself.

Question 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): The decomposition of hydrogen peroxide to form water and oxygen is an example of disproportionation reaction.
Reason (R): The oxygen of peroxide is in –1 oxidation state and it is converted to zero oxidation state in O2 and –2 oxidation state in H2O.
  1. Both A and R are true and R is the correct explanation of A.
  2. Both A and R are true but R is not the correct explanation of A.
  3. A is true but R is false.
  4. Both A and R are false.
Answer
  1. Both A and R are true and R is the correct explanation of A.

Explanation:

$2\text{H}_2\text{O}_2\text{(ag)}\xrightarrow{ \ \ \ \ \ \ \ \ }2\text{H}_2\text{O(l)}+\text{O}_2\text{(g)}$

Here the oxygen of peroxide, which is present in -1 state, is converted to zero oxidation state in O2 undergoing oxidation and decreases to -2 oxidation state in H2O undergoing reduction.

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Question 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): In the reaction between potassium permanganate and potassium iodide, permanganate ions act as oxidising agent.
Reason (R): Oxidation state of manganese changes from +2 to +7 during the reaction.
  1. Both A and R are true and R is the correct explanation of A.
  2. Both A and R are true but R is not the correct explanation of A.
  3. A is true but R is false.
  4. Both A and R are false.
Answer
  1. A is true but R is false.

Explanation:

As permanganate ion changes to MnO2.

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Question 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): Redox couple is the combination of oxidised and reduced form of a substance involved in an oxidation or reduction half cell.
Reason (R): In the representation $\text{E}^\ominus_{\text{Fe}^{3+}/\text{Fe}^{2+}}$ and $\text{E}^\ominus_{\text{Cu}^{2+}/\text{Cu}},\text{Fe}^{3+}/\text{Fe}^{2+}$ and $\text{Cu}^{2+}/\text{Cu}$ are redox couples.
  1. Both A and R are true and R is the correct explanation of A.
  2. Both A and R are true but R is not the correct explanation of A.
  3. A is true but R is false.
  4. Both A and R are false.
Answer
  1. Both A and R are true but R is not the correct explanation of A.

Explanation:

A redox couple is defined as pair of compounds or elements having together the oxidised and reduced forms of it and taking part in an oxidation or reduction half reaction.

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Question 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): Among halogens fluorine is the best oxidant.
Reason (R): Fluorine is the most electronegative atom.
  1. Both A and R are true and R is the correct explanation of A.
  2. Both A and R are true but R is not the correct explanation of A.
  3. A is true but R is false.
  4. Both A and R are false.
Answer
  1. Both A and R are true and R is the correct explanation of A.

Explanation:

Fluorine is most electronegative element that is why it is best oxidant among halogens.

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