Question

The chemical formula of calcium hydroxide is _________.

• A. $CaO{H}_2$
• B. $Ca(OH{)}_2$
• C. $C{a}_2(OH{)}_3$
• D. $Ca{O}_2$

Answer 1

The correct option is B $Ca(OH{)}_2$

Calcium hydroxide consist of calcium ion and hydroxide ion i.e. $C{a}^{2+}$ and $(OH{)}^{-}$, which have a charge of +2 and -1 respectively.
$$\begin{array}{ccc}\text{Symbol}& \text{Ca}& \text{OH}\\ \text{Charge}& \text{+2}& \text{-1}\end{array}$$
On cross-multiplication and balancing the charge, we get the formula as $Ca(OH{)}_2$.