Question

What is the empirical formula for magnesium hydroxide (milk of magnesia)?

Answer 1

`Mg(OH)_2`. Look at its position on the Periodic Table.

Explanation:

Magnesium metal lies in Group II of the Periodic Table; it readily loses 2 electrons to give rise to `Mg^(2+)`. Since hydroxide has formulation of (`OH^-`), formula for magnesium hydroxide is `Mg(OH)_2`.

What are the formulae for calcium hydroxide and barium hydroxides?

Answer 2

`"Mg"("OH")_2`

Explanation:

The thing to remember when dealing with ionic compounds is that their empirical formula is equivalent to their chemical formula .

In other words, if you know an ionic compound's chemical formula, you also know its empirical formula.

A compound's empirical formula will tell you what the smallest whole number ratio is for the atoms of the elements that make up that compound.

In the case of ionic compounds, you know that their chemical formula is given by the formula unit, which tells you the smallest whole number ratio that exist between the cations and anions that form said compound.

You know that magnesium hydroxide is composed of magnesium cations, `"Mg"^(2+)`, and hydroxide anions, `"OH"^(-)`.

In order to blance the positive charge of the cations, the formula unit of magnesium hydroxide will consist of two hydroxide anions.

`"Mg"^(2+) + 2"OH"^(-) -> "Mg"("OH")_2`

This is also the compound's empirical formula.