Homework Help: Chemistry

Posted by Sofia on Tuesday, June 23, 2009 at 12:43pm.

How do you determine the percent composition by mass of a 100 g K2SO4 solution containing a 20-g solute. What is the mole percent composition of the solute, assuming that the solution consists of 100 g water and 20 g of K2S04?

For percent composition of K2S04, I got 44.9 % K, 18.4 % S, and 36.7 % O, but I'm not sure if that's right. I have no idea how to determine the mole percent composition, though. If anyone can help me with this problem, I'll truly appreciate it!

Chemistry - David, Tuesday, June 23, 2009 at 1:25pm
For mole composition, you would convert each to moles and then determine the percent of each to the total.
Chemistry - Sofia, Tuesday, June 23, 2009 at 1:34pm
Thank you for the help : ) I just have 2 questions:
Was the percent composition for K2SO4 that I calculated correct? Also, would I convert the 20 g of K2SO4 to moles, and then find the individual moles of each element in that compound? Thanks again for the help!
Chemistry - DrBob222, Tuesday, June 23, 2009 at 3:06pm
For percent composition K, S, and O, your numbers are correct; however, I don't think that is the answer to the question. As I read the question, you have 20 g K2SO4 in 100 g solution. The question is what is the percent K2SO4. That is 20%.

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