CE Question

The answer is C.

A. No reaction occurs.
A more reactive metal would displace a less reactive metal from the solution of its salt. Since Cu is less reactive than Zn, thus Cu cannot displace Zn from ZnSO4 solution.

B. No reaction occurs.
Both reactants are neither acid/alkali nor oxidizing/reducing agents. Besides, no precipitation occurs because Ca(NO3)2 and MgCl2 are soluble in water.

C. Precipitation occurs.
Pb(NO3)2(aq) + 2NaOH(aq) → Pb(OH)2(s) + 2NaNO3(aq)
or: Pb2 (aq) + 2OH-(aq) → Pb(OH)2(s)

D. No reaction occurs.
A more reactive halogen can displace a less reactive halogen from the solution of its salt. Since Br2 is less reactive than Cl2, thus Br2 cannot displace Cl2 from NaCl solution.
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