Question

what is the balanced chemical reaction occurring when zinc metal is added to hydrofluoric acid?
partial activity series
k ca mg al zn fe ni pb h cu ag
f₂ cl₂ br₂ i₂
zn + 2hf → znf₂ + h₂
no reaction occurs.
zn + hf → znh + f
zn + hf → znf + h

Explanation:

To determine the balanced chemical reaction, we first use the activity series. Zinc (Zn) is more reactive than hydrogen (H) (from the activity series: Zn is before H). So, Zn can displace H from hydrofluoric acid (HF). The reaction is a single - displacement reaction: $Zn + HF$ (unbalanced) will form $ZnF_2$ and $H_2$. Now, balance the equation. On the left side, for HF, we need 2 moles to balance the F and H atoms. So the balanced equation is $Zn + 2HF
ightarrow ZnF_2 + H_2$. The other options are incorrect: "No reaction occurs" is wrong as Zn is more reactive than H; the other two options have incorrect products (wrong formulas or unbalanced and incorrect reaction types).

Answer:

A. $\ce{Zn + 2HF
ightarrow ZnF_{2} + H_{2}}$