How many moles are in 36.0g. of H2O?

2.0 moles

Explanation:

The relationship between the number of moles of a given substance present in a sample and the mass of the sample is given by the molar mass of the substance.

For any chemical species, you have

molar mass

=

the mass of exactly 1 mole

water has a molar mass of

18.015 g mol

−

1

which means that

1

mole of water has a mass of

18.015 g

.

18.015 g mol

−

1

=

18.015 g

1 mole H

2

O

So for every

18.015 g

of water present in your sample, you have

1

mole of water.

This means that your

36-g

sample will contain

36

g

⋅

given by the molar mass of H

2

O



1 mole H

2

O

18.015

g

=

2.0 moles H

2

O

~~~

The answer must be rounded to two sig figs, the number of sig figs you have for the mass of water.

Explanation: