Tuesday
September 1, 2015

Homework Help: science

Posted by cara on Wednesday, April 1, 2009 at 4:37pm.

I did a hydrate lab in school and these were my results and at the end we have to write the correc formula for the hydrate but I know the answer at the end is supposed to be 5H2O so why do I keep getting 4H2O? Can someone double check my work
Mass of evaporating dish 35.88


Mass of Dish and hydrated chemical 39.46


Calculated mass of hydrated chemical only 3.58


Mass of dish and chemical after 1st heating 38.40


Mass of dish and chemical after 2nd heating 38.40


Mass of dish and chemical after 3rd heating (if needed)



Now calculate the following:

Mass of anhydrous chemical only 38.40-35.88= 2.52 g


Mass of water lost. 1.06 g


% of hydrate the anhydrous chemical is. 2.52/3.58= 70.39%


Molar Mass of anhydrous Copper (II) sulfate 159. 6


226.7


Molar weight of water lost 67.2

Total number of moles of water
226.7-159.6= 67.1 67.1/18.02= 3.723 mols= 4


Prefix
tetra

Correct formula for the hydrate
CuSo4 4H20

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