### Q E27

Posted:

**Thu Oct 04, 2018 5:19 pm**Did anyone know how to find part A. I got part B but there's a step I'm missing because I have no idea where the answer from part A comes from.

Created by Dr. Laurence Lavelle

https://lavelle.chem.ucla.edu/forum/

https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=10&t=33043

Page **1** of **1**

Posted: **Thu Oct 04, 2018 5:19 pm**

Did anyone know how to find part A. I got part B but there's a step I'm missing because I have no idea where the answer from part A comes from.

Posted: **Thu Oct 04, 2018 6:10 pm**

If you start off with one molecule of water, you have to divide by Avogadro's number to convert the molecule to moles, and then you can multiply the mole by the molar mass of water to get grams. So you should end up with 2.991 x 10^-23 g/molecule. Does that make sense?

Posted: **Thu Oct 04, 2018 10:46 pm**

Since water has a molar mass of 18.02 g/mole, you can divide that by Avogadro's number in order to get g/molecule.

(18.02g/mol)/(6.022*10^23molecules/mol)=2.992*10^-23g/molecule

(18.02g/mol)/(6.022*10^23molecules/mol)=2.992*10^-23g/molecule

Posted: **Thu Oct 04, 2018 11:14 pm**

Find the weight of 1 mole of water. Remember each mole of a substance contains exactly 6.022*10^23 molecules of that substance. Therefore the weight of a mole of water divided by 6.022*10^23 would equal the weight of 1 water molecule.

Posted: **Thu Oct 04, 2018 11:55 pm**

To find the mass of one water molecule, divide it by Avogadro's number and then multiply it by the molar mass of water.