Question

4. How many molecules of H2O are there in 1.0 g of H2O?
Please help me how to do this?
:O

Answer 1

The molar weight of H2O is 18, because Hydrogen weighs 1g/mol, and Oxygen weighs 16g/mol. Therefore, to find the number of moles of H2O in one gram, divide the given amount by the molar weight.
\[\frac{ 1 }{ 18 }mol\]

Answer 2

Grams to moles to molecules.

1.0 g H20 * 1 mol/18.016 grams H20 *

6.022 X 10^23 molecules/1 mol H20 =

number of molecules in 1 gram of H20

Does that make sense? :)

Answer 3

First calculate the amount of mol H2O.
H=1.00794 g/mol
O=15.9994 g/mol
So the molecular weight of H2O = (2*1.00794)+15.9994= 18.01528 g/mol

18.01528 grams = 1 mol.
So 1 gram = 1/18.01528 = 0.0555 mol H2O

Multiply that by Avogadro's number ( 6.0221413*10^23 )

0.0555 * 6.0221413*10^23 = the number of molecules in 1 gram H2O