How many atoms of H are in 93.2 grams of PH3?

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

*

1.00794

g/mol

18.0153

g/mol

*

100

=

11.19

%

This means that every

100 g

of water will contain a total of

11.19 g

of hydrogen. Since your sample has a mass of

23.5 g

, it follows that it will contain

23.5

g water

⋅

11.19 g H

100

g water

=

2.63 g H

Alternatively, you can first find the number of moles of water in get in that

23.5 g

sample

23.5

g

⋅

1 mole H

2

O

18.0153

g

=

1.3044 moles H

2

O

SInce one molecule of water contais 2 atoms of hydrogen, you will get

1.3044

moles water

⋅

2 moles H

1

mole water

=

2.6088 moles H

Finally, use hydrogen's molar mass to find how many grams would contain this many moles

2.6088

moles

⋅

1.00794 g H

1

mole

=

2.63 g

Answer: 2.63

Explanation:

One way to approach this problem is to determine the percent composition of hydrogen in water.