How many grams of H are there in 23.5 g of #H_2O#?
1 Answer
Explanation:
One way to approach this problem is to determine the percent composition of hydrogen in water.
You know that one water molecule contains
- one oxygen atom
- two hydrogen atoms
This means that every mole of water molecules will contain 2 moles of hydrogen and 1 mole of oxygen atoms.
To find the percent composition of hydrogen in water, use the molar mass of water and that of hydrogen
#(2 xx 1.00794color(red)(cancel(color(black)("g/mol"))))/(18.0153color(red)(cancel(color(black)("g/mol")))) xx 100 = 11.19%#
This means that every
#23.5color(red)(cancel(color(black)("g water"))) * "11.19 g H"/(100color(red)(cancel(color(black)("g water")))) = color(green)("2.63 g H"#
Alternatively, you can first find the number of moles of water in get in that
#23.5color(red)(cancel(color(black)("g"))) * ("1 mole H"_2"O")/(18.0153color(red)(cancel(color(black)("g")))) = "1.3044 moles H"_2"O"#
SInce one molecule of water contais 2 atoms of hydrogen, you will get
#1.3044color(red)(cancel(color(black)("moles water"))) * "2 moles H"/(1color(red)(cancel(color(black)("mole water")))) = "2.6088 moles H"#
Finally, use hydrogen's molar mass to find how many grams would contain this many moles
#2.6088color(red)(cancel(color(black)("moles"))) * "1.00794 g H"/(1color(red)(cancel(color(black)("mole")))) = color(green)("2.63 g H")#