Where am I wrong in my calculations? [closed]








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I am revisiting the concept of mole and I decided to figure out random values (for instance: mass of 1 molecule of water) to see how much I understand the concept of moles and how it relates to amu. So here is how I started:


There is 1 mole of C atoms in 12g of C and 1 C atom is 12 amu. Therefore, there is 1 mole of 1 amu in 1g. That means there are 6.02e23 nucleons in 1 gram. So, 1 nucleon is 1g/6.02e23= 1.66e-24g. A molecule of water has 14 nucleons (6 neutrons and 6 protons from oxygen and 2 protons from both H); thus, 1.66e23 x 14 should be the g of a water molecule, which turns out to be 2.33e-23. However, this is not the correct mass of water molecule (2.992 x 10¯23 grams). 




As Ivan pointed out in the comments, I had the molar mass of water incorrect. By fixing the molar mass to 18g/mol, I get the correct answer.


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