Aqueous solutions of acids react in four general ways to make a salt. The first part of the salt name is the metal, and the second part comes from the acid. Hydrochloric acid makes chlorides, sulfuric acid makes sulfates and nitric acid makes nitrates. In each reaction the hydrogen of the acid is replaced by the metal.
- Acid + metal → salt + hydrogen. For example, magnesium + sulfuric acid → magnesium sulfate + hydrogen. Only metals reactive enough, such as magnesium, zinc and iron, react like this.
- Acid + metal oxide → salt + water. For example, zinc oxide + hydrochloric acid → zinc chloride + water.
- Acid + metal hydroxide → salt + water. For example, sodium hydroxide + nitric acid → sodium nitrate + water.
- Acid + metal carbonate → salt + water + carbon dioxide. For example, calcium carbonate + hydrochloric acid → calcium chloride + water + carbon dioxide.
You can see bubbles of gas when an acid reacts with a metal or a carbonate. There are no bubbles when an acid reacts with an oxide or a hydroxide, because only water forms.