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 Posted: Thu Dec 06, 2007 8:48 pm
Hey, can anyone help me out here? I know this is a Physics and Math guild, but does anybody know some Chemistry stuff too? Cause I can't figure out how to do these problems...Here they are, and if you guys don't know how to do them, can you please refer me to someone who does? Thanks...
Calculate the percentage of water in each of the following hydrates:
a) sodium carbonate decahydrate, Na2CO3*10H2O
b) nickel (II)iodide hexahydrate, NiI2*6H2O
c) ammonium hexacyanoferrate (III) trihydrate (aka ammonium ferricyanide), (NH4)2Fe(CN)6*3H2O
d) aluminum bromide hexahydrate
...Anybody got a clue??? sweatdrop neutral lol
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Posted: Fri Dec 07, 2007 11:26 pm
Percent mass is what'd I guess you're looking for.
So, find the total molar mass of the molecule, then using the individual molar masses of the atoms, found out how many percent the water is by dividing the total molar mass by the combined mass of all of the water, then multiplying your result by 100.
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Posted: Thu Mar 27, 2008 6:22 am
What he said.
Stepwise:
1) Find molar mass of Na2CO3 (sorry about the lack of subscripts)... this is about 106, I think.
2) Find molar mass of 10 H20s. This is about 10*18, so 180.
3) Add these together. You get 286.
4) Take Step 2 and divide it by Step 3. 180/286. This is the amount of water relative to the amount of total stuff. 180/286 is about .63
5) Multiply by 100% to get your percentage from the decimal. .63*100% = 63%
Does that help?
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