## 6th Edition E27, First Part

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Te Jung Yang 4K
Posts: 63
Joined: Fri Sep 28, 2018 12:18 am

### 6th Edition E27, First Part

I'm stuck on the first part of the question in title. How do you convert 1 H20 molecule to moles?

Kyle Golden Dis 2G
Posts: 67
Joined: Fri Sep 28, 2018 12:17 am

### Re: 6th Edition E27, First Part

All you do is divide 1 by Avogadro's number. The calculation should looks like this: 1/(6.02 x 10^23).

KylieY_3B
Posts: 31
Joined: Fri Sep 28, 2018 12:24 am

### Re: 6th Edition E27, First Part

You divide 1 H2O molecule by Avogadro's constant (6.02 * 10^23) to convert to moles, then multiple by molar mass to convert to grams.

Te Jung Yang 4K
Posts: 63
Joined: Fri Sep 28, 2018 12:18 am

### Re: 6th Edition E27, First Part

Oh hey, quick reply guys! Thanks. To catch you guys here, is the reason why it is 1 / (6.022 x 10^23) moles because of the need to cancel out the units via dimensional analysis?

Angel Chen 2k
Posts: 59
Joined: Fri Sep 28, 2018 12:20 am

### Re: 6th Edition E27, First Part

you use the Avogadro's constant to convert from mass per mol to mass per molecule. It should be (1/6.022x10^23 molecules.mol^-1 ) so you would be able to get g.molecule^-1 for the mass of the H2O molecule.

305144105
Posts: 32
Joined: Thu May 10, 2018 3:00 am

### Re: 6th Edition E27, First Part

Converting one H2O molecule to moles using dimensional analysis:
=1 molecule * 1 mol / 6.022*10^23 molecules
=1.66 * 10^-24 mol of H2O

Solving E27(a) using dimensional analysis:
Mass of 1 water molecule = (1.008*2 + 15.999)g/1mol * 1mol/6.022*10^23 molecules = 2.99 * 10^-23 g

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