Which of the following elements would displace copper from a solution of copper ions?

Step 1: Analyze the question We are asked which element can displace copper from a solution containing Cu²⁺ ions. This is a displacement reaction, and it depends on the reactivity series.

Step 2: The concept A more reactive metal displaces a less reactive metal from a solution of its salt. The reactivity series (most to least reactive) is:

K > Na > Ca > Mg > Al > Zn > Fe > Sn > Pb > H > Cu > Hg > Ag > Au

So, to displace copper, the metal must sit above copper in the series.

Step 3: Check each option

• A. Silver: below copper, so it cannot displace copper.
• B. Gold: below copper (one of the least reactive metals), so it cannot displace copper.
• C. Lead: above copper, so it can displace copper.
• D. Mercury: below copper, so it cannot displace copper.

Step 4: The reaction Pb(s) + Cu²⁺(aq) → Pb²⁺(aq) + Cu(s)

Lead loses electrons (it is oxidised) and copper ions gain electrons (they are reduced). This agrees with the electrode potentials: E° for Pb²⁺/Pb is about −0.13 V, while Cu²⁺/Cu is about +0.34 V, so the reaction is feasible.

(In practice, lead reacts slowly in some solutions because insoluble lead salts can coat the surface, but in terms of the reactivity series, lead is the only option that can displace copper.)

Answer: C. Lead

Exam tip: Remember the series with the mnemonic "Please Stop Calling Me A Zebra In Love Here, Copper Silver Gold." Anything to the left of copper can displace it. For these questions, just locate the metals in the series and compare positions.