## Fundamentals Textbook Homework E.23 part D

Anna_Mohling_1D
Posts: 70
Joined: Wed Sep 30, 2020 9:56 pm

### Fundamentals Textbook Homework E.23 part D

Calculate the amount (in moles) of (d) H2O in 2.00 g of Na2CO3⋅10H2O

For this question, I found the molar mass of Na2CO3⋅10H2O to be 19100 g. mol^-1. I divided 2g by this molar mass to get 1.05x10^-4 moles Na2CO3⋅10H2O. I then multiplied this by 10 because there are 10 (molecules?) of H2O to get 0.00105 moles of H2O.

My answer is wrong, and I think I went wrong when multiplying by 10 but I am unsure how else to get the moles of just H2O. Any help would be greatly appreciated!

Samantha Pedersen 2K
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Joined: Wed Sep 18, 2019 12:21 am
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### Re: Fundamentals Textbook Homework E.23 part D

It looks like you may have calculated the molar mass of Na2CO3⋅10H2O incorrectly. The molar mass of Na is 22.99 g/mol, the molar mass of C is 12.01 g/mol, the molar mass of oxygen is 15.99 g/mol, and the molar mass of water is 18.02 g/mol. When you multiply these numbers by the number of their respective atoms/molecules in the compound, you should get a molar mass of 286.21 g/mol. All of the other steps you followed are correct! I hope this helps!

Natalie Do 3F
Posts: 77
Joined: Wed Sep 30, 2020 10:03 pm

### Re: Fundamentals Textbook Homework E.23 part D

The molar mass is 286.21 g/mol
2g x (1mol/286.21 g) x (10mol h2o/1mol Na2CO3⋅10H2O) = .0699 mol H2O