Explain why the reactivity series must be used for single replacement reactions, but not for double replacement.

Here's what I get  

Explanation:

In a single replacement reaction, one element must displace another element from its compound.

Thus, we must consider the reactivity series, because an element lower down in the series cannot replace one that is above it.

In a double replacement reaction, the cations change partners with the anions. All we need consider are the solubilities of the new cation-anion partners.

In a single replacement reaction, it is mandatory that one element displaces the other according to their reactivity on the reactivity series.

On the other hand, In a double- displacement reaction; the cations just exchange anions and vice versa.

An example of a single displacement reaction is;

An example of a double displacement reaction is;

As such, there's no preference in double displacement reactions as ions are swapped.

Read more:

link

acid rain does not usually kill trees directly. instead, it is more likely to weaken the trees by damaging their leaves, limiting the nutrients available to them, or poisoning them with toxic substances slowly released from the soil. the main atmospheric pollutants that affect trees are nitrates and sulphates.