identification code of unknown _____ determination mass of crucible plus sample,

Question

identification code of unknown _____ determination mass of crucible plus sample, g ____ ____ mass of empty crucible, g _____ ______ mass of hydrate sample, g _____ ______ mass of crucible and sample: after first heating and cooling, g ______ _____ after second heating and cooling, g ______ ______after third heating and cooling. g ____ _______ mass of water lost, g ______ _____ mass percent of water in sample, % _____ ____ formula of anhydrous salt ____ molar mass of anhydrous salt, g mol^-1 ______ mass of anhydrous salt, g ____ _____ number of moles of anhydrous salt remaining in the crucible, mol ______ ____ number of moles of water lost, mol _____ ____ average number of moles of water per mole of hydrate, mol _____ formula of hydrate ______

Explanation / Answer

Trial 1:

mass of hydrate = (Mass of cruicible + sample) - (mass of cruicible)

mass of hydrate = (19.965-18.245) = 1.72

then

mass of water lost = Mass of hydrate - Mass of sample after heating = 19.965-19.315 = 0.65 g of water

% mass of wterr = mass of water / total mas * 100% = 0.65 / 1.72*100 = 37.8% is water

anhydrous mass:

CuSO4 * xH2O

mol of waster = 0.65/18 = 0.03611 mol of Water

mol of CusO4 = (1.72-0.65)/(159.609 ) = 0.00670 mol of CuSO4

ratio

0.03611 /0.00670 = 5.38

nearest is 5

so

CusO4*5H2O

Molar Mass of Anhydrous salt = CusO4 = 159.609 g/mol

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