ATAR Notes: Forum
VCE Stuff => VCE Science => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Chemistry => Topic started by: Einstein on March 03, 2014, 08:17:46 pm
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A 1.124 g sample of CaSO4 crystals was heated to drive off the water of crystallisation. When completely dry, a residue of 0.889 g was obtained. Determine the empirical formula of the hydrated compound.
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A 1.124 g sample of CaSO4 crystals was heated to drive off the water of crystallisation. When completely dry, a residue of 0.889 g was obtained. Determine the empirical formula of the hydrated compound.
Heating crystal to drive off water meaning 0.889 is the mass of anhydrous (= no water ) crystals. Hence, you have mass of crystals, subtract it from the total mass, you have the mass of water that has been driven off. From here, use n=m/M, find the mole ratio between crystals and water and determine empirical formula. Try this out, you should get CaSO4.2H2O
Hope this helps.
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yeah i was stupid and did 0.235/1 (which is hydrogen) forgot to do 0.235/18 (H20)