Final answer:
In the proposed reaction, Cl2(g) + 2HF(aq), a single-replacement reaction is not expected to occur because fluorine is more reactive than chlorine, meaning chlorine cannot displace fluorine from hydrofluoric acid.
Step-by-step explanation:
For a single-replacement reaction to occur, a more reactive element typically displaces a less reactive element from a compound.
In this case, elemental chlorine (Cl2) is reacting with hydrofluoric acid (HF). The reactivity of halogens decreases down the group (F > Cl > Br > I), so chlorine would not usually displace fluorine from HF.
Therefore, we would not expect a reaction of the form Cl2(g) + 2HF(aq) → H2 + 2ClF to occur because fluorine is more reactive than chlorine.
However, if we consider another similar reaction, like Cl2 + 2Na+(aq) + 2Br−(aq) → 2Na+(aq) + 2Cl−(aq) + Br2(l), the chlorine can displace the bromide ions since chlorine is more reactive than bromine.