JEE Main 2015 · 10 Apr · Shift 1 · Chemistry Q38

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ChemistrySingle correct+4 / -1Question 38 of 90

A variable, opposite external potential ( $E_{ext}$ ) is applied to the cell $\ce{Zn | Zn^2+ (1 M) || Cu^2+ (1 M) | Cu}$ , of potential 1.1 V. When $E_{ext}<1.1$ V and $E_{ext}>1.1$ V, respectively electrons flow from :

anode to cathode and cathode to anode

cathode to anode and anode to cathode

cathode to anode in both cases

anode to cathode in both cases

Answer and worked solution

Official answer: D

Electrons always go into the external circuit at the anode.

For $E_{ext}<1.1$ V the cell discharges: Zn is the anode, and electrons flow from Zn to Cu.
For $E_{ext}>1.1$ V the cell is driven backwards, and Cu becomes the anode.

In both cases, relative to the electrode acting as anode at the time, electrons flow from anode to cathode.

Topics:Galvanic cells and EMF

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JEE Main 2015 · 10 Apr · Shift 1, Chemistry question 38