A single replacement reaction, sometimes called a single displacement reaction, is a reaction in which one element is substituted for another element in a compound. The starting materials are always pure elements, such as a pure zinc metal or hydrogen gas, plus an aqueous compound.
when carbon dioxide gas is collected down ward of water wet gas is collected by the downward displacement of water . This is used for gases that are not very soluble in water . ... In water , carbon dioxide produces a weakly acidic solution , carbonic acid .
