single-replacement reactions and a double-replacement reactions differ in the fact that in a single-replacement reaction only one element that has a positive charge is oxidized or looses electrons....
When a compound is mixed with an element. KCl is more than one element put together, thus it is a compound. Sodium (Na) is an element, so if you combine the two, it is a single replacement reaction.
A single replacememt reaction is a reaction in which the atoms of one element replace the atoms of another element in a compound. The following chemical equation describes thisA+ BX ------> AX + B...