In a single-displacement reaction, one element displaces another element in a compound. The general form of a single-displacement reaction is:

```

A + BC → AC + B

```

where A is the displacing element, B is the element being displaced, and C is the anion (negative ion) of the compound.

For example, when iron (Fe) is added to copper sulfate (CuSO4), the iron displaces the copper from the compound, forming iron sulfate (FeSO4) and copper metal (Cu).

```

Fe + CuSO4 → FeSO4 + Cu

```

Double-displacement reaction:

In a double-displacement reaction, two elements in two different compounds exchange places. The general form of a double-displacement reaction is:

```

AB + CD → AD + CB

```

where A and C are the cations (positive ions) of the compounds, and B and D are the anions.

For example, when sodium chloride (NaCl) is added to silver nitrate (AgNO3), the sodium and silver ions exchange places, forming sodium nitrate (NaNO3) and silver chloride (AgCl).

```

NaCl + AgNO3 → NaNO3 + AgCl

```

How to determine if a reaction is a single-displacement or double-displacement reaction:

To determine if a chemical reaction represents a single-displacement or double-displacement reaction, look at the number of reactants and products. In a single-displacement reaction, there are two reactants and two products. In a double-displacement reaction, there are four reactants and four products.

Additionally, in a single-displacement reaction, one element is displaced by another element. In a double-displacement reaction, two elements in two different compounds exchange places.