Posted by A Canadian on Thursday, February 7, 2013 at 11:16pm.
I don't really understand why unit analysis works.
I found a simple example on a website (I can post the link in a comment if you want).
For example, convert 18 grams of water to moles. The molar mass of water is 18 g/mol; therefore :
18g H2O x 1 mol/18g H2O = 1 mol H2O
In 1 mol/18g H2O, I get that the denominator is molar mass, but how come the regular unit, g/mol, isn't used and just g is used? How come we're able to do that?
And what does this equation mean in words.. ?
There's 18g H2O for every 1mol of H2O (which weighs 18g)... So there's 1 mol of H2O...?
Chemistry - A Canadian, Thursday, February 7, 2013 at 11:18pm
But I don't think division would mean "which" weighs 18g..
Chemistry - DrBob222, Thursday, February 7, 2013 at 11:46pm
The molar mass is defined in simple terms as the mass of a mole plus the word "grams".
Chemistry - A Canadian, Thursday, February 7, 2013 at 11:54pm
, but then would 1mol/18g H2O mean
1 mol per 18 grams per mol of H2O..? There's one mol for every 18g of H2O..? It's confusing
Chemistry - DrBob222, Friday, February 8, 2013 at 12:10am
1 mol H2O is 18 grams. The factor used in dimensional analysis is 1 mol H2O/18 g H2O or 18g H2O/1 mol H2O.
1 mol/18 g H2O means 1 mol H2O/18 g H2O. I don't understand what's confusing about "There's one mol (of water) for every 18 g of H2O." Perhaps my (of water) addition helps clarify the statement.
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