Hydroxide
The solubility in water of the other hydroxides in this group increases with increasing atomic number. Magnesium hydroxide Mg(OH) is a strong base (up to the limit of its solubility, which is very low in pure water), as are the hydroxides of the heavier alkaline earths: calcium hydroxide, strontium hydroxide, and barium hydroxide. A solution or suspension of calcium hydroxide is known as limewater and can be used to test for the weak acid carbon dioxide. The reaction Ca(OH) + CO Ca + + OH illustrates the basicity of calcium hydroxide. Soda lime, which is a mixture of the strong bases NaOH and KOH with Ca(OH), is used as a CO absorbent.
Hydride
In chemistry, a hydride is the anion of hydrogen, H, or, more commonly, it is a compound in which one or more hydrogen centres have nucleophilic, reducing, or basic properties in it. In compounds that are regarded as hydrides, the hydrogen atom is bonded to a more electropositive element or groups. Compounds containing hydrogen bonded to metals or metalloid may also be referred to as hydrides. Common examples are ammonia (NH), methane (CH), ethane (CH) (or any other hydrocarbon), and Nickel hydride (NiH), used in NiMH rechargeable batteries.