MediumChemistryHigh School (11–12)Redox Reactions › Oxidation Number and Types of Redox ReactionsConceptualA-Level AP IB NEET

A student joins a zinc half-cell to a standard hydrogen electrode…

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Try it on paper first. A hint, the key idea and the worked solution are here when you need them.

A student joins a zinc half-cell to a standard hydrogen electrode. The voltmeter reads $0.76\ \text{V}$ and the zinc is the negative terminal. (a) Name the conditions for the zinc half-cell and for the hydrogen electrode. (b) Write the sign and size of $E^\circ$ for $\text{Zn}^{2+}/\text{Zn}$ and explain it.

Need a reminder? The key ideaShow

$E^\circ$ is a reduction potential, measured against the standard hydrogen electrode, which is $0.00\ \text{V}$ , at $1\ \text{mol/L}$ , $1\ \text{bar}$ and $298\ \text{K}$ . $E^\circ_{cell} = E^\circ_{cathode} - E^\circ_{anode}$ . Reversing a half-reaction changes the sign of $E^\circ$ . Multiplying it changes nothing.

The worked solution

Have you tried it?

Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.

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← A silver half-cell has E° = +0.80 V and an iron half-cell has E° = -0.44 V…For Zn²⁺(aq) + 2e⁻ → Zn(s), the standard electrode potential is -0.76 V… →

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