# What is the mass of hydrogen in one mole of aluminum hydroxide?

## The molar mass of hydrogen is 1.01 g/mol

Aug 7, 2016

$\text{3.03 g}$

#### Explanation:

The first thing to do here is figure out the chemical formula for aluminium hydroxide.

Aluminium is located in group $13$ of the periodic table, and forms $3 +$ cations, ${\text{Al}}^{3 +}$. The hydroxide anion, ${\text{OH}}^{-}$, carries a $1 -$ charge, which means that a formula unit of aluminium hydroxide will look like this

${\left[\text{Al"^(3+)] + color(blue)(3)["OH"^(-)] -> "Al"("OH}\right)}_{\textcolor{b l u e}{3}}$

Now, you can figure out the mass of hydrogen present in $1$ mole of aluminium hydroxide by first determining how many moles if hydrogen you get in $1$ mole of aluminium hydroxide.

Since $1$ mole of aluminium hydroxide contains $\textcolor{b l u e}{3}$ moles of hydroxide anions, which in turn contain $1$ mole of hydrogen each, you can say that you will have

$\text{1 mole Al"("OH")_ color(blue)(3) -> color(blue)(3)color(white)(a)"moles OH"^(-) -> color(blue)(3)color(white)(a)"moles H}$

The problem tells you that the molar mass of hydrogen is equal to ${\text{1.01 g mol}}^{- 1}$. This means that $1$ mole of hydrogen has a mass of $\text{1.01 g}$.

You can thus say that one mole of aluminium hydroxide contains

color(blue)(3)color(red)(cancel(color(black)("moles H"))) * "1.01 g"/(1color(red)(cancel(color(black)("mole H")))) = color(green)(|bar(ul(color(white)(a/a)color(black)("3.03 g H")color(white)(a/a)|)))

I'll leave the answer rounded to three sig figs.