November 28, 2015

Homework Help: Chemistry

Posted by anonymous on Tuesday, July 31, 2007 at 10:36pm.

1)The chemical formula for aspirin is C9H8O4. What is the mass of 0.40 mol of aspirin? How would I find this?

2)The gram molecular mass of oxygen is 16.0 g right?

3)How would I find the mass, in grams, of 3.01 x 10^23 molecules of water?

1. Add the atomic masses of the elements in the formula. That will be 1 mol. Then 0.4 of that will be 0.4 mol.

2. One mol (of anything) contains 6.02 x 10^23 molecules. So find the mols in 3.01 x 10^23 molecules and that times the molar mass of H2O (obtained by adding the atomic masses) will be that many grams.

Post your work if you get stuck.

1 mol of oxygen atoms has a mass of 16 grams.

water is H2O. One mol of water thus has a mass of approximately 18 grams

The mass of of 3.01 x 10^23 molecules of water is:

(3.01 x 10^23/mol) times the mass of one mol of water =

(3.01 x 10^23/mol) 18 grams.

Now, what is 3.01 x 10^23 divided by 1 mol?

1 mol = approximately 6.022*10^23

Question 1:

1 mol of C9H8O4 contains

9 moles of C, 8 moles of H and 4 moles of O. The mass of 1 mol of aspirine is thus:

(9*12 + 8 + 4*16) grams

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