Whats the answer?

Question

Are any of these equations redox reactions? if so what are their reducing and oxidizing agents?

CuSO₄(aq)+Zn(s)→ZnSO₄(aq)+Cu(s)

HCl(aq)+NH₃(aq)→NH₄Cl(aq)

2Ca(s)+O₂(g)→2CaO(s)

Answer 1

The first reaction is definitely a redox reaction. The copper in CuSO₄ has a oxidation number of +2, as it is bound to a sulfate ion with a number of -2. The zinc reactant is in its pure elemental state, meaning it has an oxidation number of 0. After the reaction takes place, the copper is now in its pure elemental form, meaning it has gone from +2 to 0. The zinc, now bound with the sulfate ion, takes on an oxidation number of +2, the sulfate not changing its number. Since the Cu is going from +2 to 0, it is gaining two electrons, meaning it has been reduced. By accepting electrons and being reduced, it is the oxidizing agent because it allows the zinc to get oxidized. The zinc goes from 0 to +2, meaning it has lost two electrons which makes it oxidized. The product getting oxidized is the reducing agent, so that would make zinc the reducing agent.

The second reaction is a synthesis reaction and does not show any change in oxidation number, meaning it is not a redox reaction. The chlorine is bound to hydrogen in its initial form, giving the Cl an oxidation number of -1. When it is bound to the NH₄ ion after the reaction, it still has an ox. number of -1. Nothing has changed and no electrons have been gained or lost.

The third reaction is also a redox reaction. To start, the calcium and oxygen are both in their pure elemental form, meaning they have ox. numbers of 0. Even though the oxygen is diatomic, it would not, for example, have a charge of +2 on one atom and -2 on the other. We assume for all diatomic molecules that the electrons are shared evenly, since both atoms have the same properties. Once the reaction takes place however, the oxygen drops to a -2 ox. number and the calcium goes to a +2 ox. number. Since the calcium goes from 0 to +2 by switching from an elemental state to a bonded state, it has lost two electrons, is oxidized, and is therefore the reducing reagent. The oxygen, going from 0 to -2 has gained two electrons, meaning it is reduced and it is therefore the oxidizing reagent.

Hope this helps!