Question

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

The molar mass of hydrogen is 1.01 g/mol

Answer 1

`"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, `"Al"^(3+)`. The hydroxide anion, `"OH"^(-)`, carries a `1-` charge, which means that a formula unit of aluminium hydroxide will look like this

`["Al"^(3+)] + color(blue)(3)["OH"^(-)] -> "Al"("OH")_color(blue)(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 `color(blue)(3)` moles of hydroxide anions, which in turn contain `1` mole of hydrogen each, you can say that you will have

`"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 `"1.01 g mol"^(-1)`. This means that `1` mole of hydrogen has a mass of `"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.