Answer:
1.635
⋅
10
24
molecules
Explanation:
In order to figure out how many molecules of water are present in that
48.90-g
sample, you first need to determine how many moles of water you have there.
As you know, a mole is simply a very large collection of molecules. In order to have one mole of something, you need to have exactly
6.022
⋅
10
23
molecules of that something - this is known as Avogadro's number.
In order to get to moles, you must use water's molar mass. A substance's molar mass tells you the mass of one mole of molecules of said substance.
Water has a molar mass of
18.015 g/mol
. This means that one mole of water molecules has a mass of
18.015 g
.
So, to sum this up,
6.022
⋅
10
23
molecules of water will amount to
1 mole
of water, which in turn will have a mass of
18.015 g
.
