Posted by denise on Tuesday, October 27, 2009 at 8:49pm.
this is for a lab - determining the chemical formula of a hydrate.
suppose the hydrate was heated too quickly and some of it was lost of spattered out of the container.
explain how hthis would effect
a) the calculated percent by mass of water in the compound
b) the molecular formula u determined
- chemistry - DrBob222, Tuesday, October 27, 2009 at 10:05pm
a). It's easier to explain with an example. Suppose we start with MgSO4.xH2O and we want to determine x.
Suppose we took a 10.000 g sample of MgSO4.xH2O and it lost 5.116 g on heating. So the water content is 5.116 g and the MgSO4 content is 10.000 - 5.116 = 4.884 g.
Here is what we do.
5.116/18.015 = 0.284 = moles H2O.
4.884/120.37 = 0.0406 = moles MgSO4.
Then 0.284/0.0406 = 7 so the formula is
NOW, if we heated too fast and some of the sample spattered, what happens. When you reweigh the sample too much mass has been lost, so the mass H2O is too high and when you subtract from 10.000, the mass of MgSO4 too low. So the percent H2O is too high (70% using the numbers from b part) and the MgSO4 is too low (30% using the numbers from b part).[Percent MgSO4 should be 48.84% and percent H2O should be 51.16%.]
b) Suppose the loss in spattering is 7.0 g just to make things simple. Then mass H2O = 7 g and 10-7 = 3 g MgSO4.
and 3/120 = 0.025, then
0.389/0.025 = 15.6 which we might round to 16 and the formula would be MgSO4.16H2O.
I hope this helps.
Answer This Question
More Related Questions
- chemistry - suppose the hydrate was heated too quickly and some of it was lost ...
- chemistry - suppose you heat a hydrate too quickly and some of it was lost as it...
- chemistry - In the experiment, a hydrate is heated to form an anhydrate. The ...
- chemistry - A 2.50 g sample of a hydrate of calcium sulphate losses 0.523 g of ...
- chemistry - A 2.500 gram sample of hydrate of calcium sulfate loses 0.532 grams ...
- science - I did a hydrate lab in school and these were my results and at the end...
- chemistry - Cobalt(2) chloride is commonly obtained from chemical supply houses ...
- Chemistry - After 0.6523 g of CoCl2*6H2O is heated, the residue has a mass of 0....
- chemistry - A 2.50g sample of a hydrate of calcium nitrate was heated, and only ...
- chemistry - a 5.00g sample of a hydrate of barium chloride was heated, and only ...