There this thing and this other thing made of things.
Single replacement occurs when there are multiple reactants that combine in a way that something in one compound is replaced by the other reactant.
A single thing replaces something in a compound.
What this looks like:
AB + C --> A + BC
A + BC -> AB + C
- In single replacement, at least one of the products and one of the reactants has to be a compound.
2K + 2H2O --> H2 + 2KOH
where the K takes the place of one H.
2Ag + H2S --> Ag2S + H2
where the Ag takes the place of the H.