How do you change mol to grams?
You multiple the mole value of the element or compound by the molar mass.
For example, if you have 2.00 moles of water,
This is accomplished by multiplying 2.0 moles of water by the molar mass of water which is 18 g/mole.
Remember that the molar mass is obtained by adding the molar masses of gram formula masses of the individual elements.
The water molecule contains 2 hydrogen atoms
The molar mass of hydrogen is 1.0 g/mol. If you have 2 hydrogen atoms, the molar of these two atoms is 2.0 g/mol.
The water molecule has 1 oxygen atom which has a molar mass of 16.0 g/mol.
If you add 2.0 and 16.0, you obtain a molar mass of 18.0g/mol.