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

Answer:

#"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.