How can you calculate molecular weight?
Let's look at the example of water. I'll round average atomic masses to two places beyond the decimal. You should adjust your rounding based on your teacher's preferences.
H = 1.01 (use the average atomic mass from the periodic table)
O = 16.00
To find molecular weight:
H = 1.01 x 2 = 2.02 (have to multiply by two since water has two hydrogen atoms)
O = 16.00 x 1 = 16.00
The total molecular weight is 18.02 - this was found by adding the total mass from H with the total mass from O.
This will also be the molar mass of water
Here are a couple more examples:
Hope this helps