A voltaic cell is made by connecting two half cells represented by half equations below : Sn²+(aq) + 2e^- → Sn(s) E°= -0.14 V Fe³+(aq) + e^- → Fe²+(aq) E°= +0.77 V Which statement is correct about this voltaic cell ? (A) Fe²+ is oxidised and the voltage of the cell is –0.91 V (B) Sn is oxidised and the voltage of the cell is 0.91 V (C) Fe²+ is oxidised and the voltage of the cell is 0.91 V (D) Sn is oxidised and the voltage of the cell is 0.63 V

ChemistryCBSE Class 12 · Board exam 2023, set 56/5/1 · 1 mark · MCQ

CBSE Class 12 Chemistry 2023: question 3

Set in the CBSE Class 12 board exam of 2023, paper 56/5/1, section A, question 3, for 1 mark. Try it first; the hints and our step-by-step solution are below.

Q3 · 1 mark · MCQElectrochemistry

A voltaic cell is made by connecting two half cells represented by half equations below :
$S n_{(aq)}^{2 +} + 2 e^{-} \to S n_{(s)}$ $E^{\circ} = - 0.14$ V
$F e_{(aq)}^{3 +} + e^{-} \to F e_{(aq)}^{2 +}$ $E^{\circ} = + 0.77$ V
Which statement is correct about this voltaic cell ?

(A) $F e^{2 +}$ is oxidised and the voltage of the cell is –0.91 V
(B)Sn is oxidised and the voltage of the cell is 0.91 V
(C) $F e^{2 +}$ is oxidised and the voltage of the cell is 0.91 V
(D)Sn is oxidised and the voltage of the cell is 0.63 V

Source: official question paper from cbse.gov.in (PDF). See it in the full 2023 board paper, set 56/5/1.

Hints

Open one hint at a time and try again before the next.

Hint 1

The half cell with the more negative $E^{\circ}$ becomes the anode.

Hint 2

Use $E_{ce l l}^{\circ} = E_{c a t h o d e}^{\circ} - E_{an o d e}^{\circ}$ .

Step-by-step solution

Each step shows the marks it earns, as an examiner would award them. Checked by an independent re-solve from the question paper.

The couple with the lower reduction potential acts as the anode. So Sn is oxidised to $S n^{2 +}$ , and $F e^{3 +}$ is reduced to $F e^{2 +}$ .
$E_{ce l l}^{\circ} = E_{c a t h o d e}^{\circ} - E_{an o d e}^{\circ} = 0.77 - (- 0.14) = 0.91$ V
1 mark

Answer: (B)

Where the marks are

Identifies Sn as the species oxidised and $E_{ce l l}^{\circ} = 0.91$ V (1 mark)

Revise the chapter

Chapter: Electrochemistry (notes, formulas, where marks are lost and every past question)

Practise this chapterBoard-style questions from Electrochemistry, one at a time, marked against the answer key and marking points.Back to the full paper2023 board paper, set 56/5/1: every question, by section.

The question is transcribed from the official paper; figures are described in words. The solution, hints and chapter tag are ours. Spotted an error? Write tosupport@questionbuddy.in.

CBSE Class 12 Chemistry 2023: question 3

Hints

Step-by-step solution

Revise the chapter

More questions from Electrochemistry