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

The molar mass of hydrogen is 1.01 g/mol

1 Answer
Aug 7, 2016

"3.03 g"3.03 g

Explanation:

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

Aluminium is located in group 1313 of the periodic table, and forms 3+3+ cations, "Al"^(3+)Al3+. The hydroxide anion, "OH"^(-)OH, carries a 1-1 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)[Al3+]+3[OH]Al(OH)3

Now, you can figure out the mass of hydrogen present in 11 mole of aluminium hydroxide by first determining how many moles if hydrogen you get in 11 mole of aluminium hydroxide.

Since 11 mole of aluminium hydroxide contains color(blue)(3)3 moles of hydroxide anions, which in turn contain 11 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"1 mole Al(OH)33amoles OH3amoles H

The problem tells you that the molar mass of hydrogen is equal to "1.01 g mol"^(-1)1.01 g mol1. This means that 11 mole of hydrogen has a mass of "1.01 g"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.