Today in chemistry we performed a mini lab that involved Copper (II) Sulfate Pentahydrate, a compound that is a deep blue color but turns a white/grey color when heated. We were trying to find the percentage of the hydrate composition and to start this process you must mass everything. This would include the evaporating dish itself, which we got 79.01 g, then we must mass the evap dish with the substance, 81.03 g, and then the mass after the first, second and third heatings, after the first heating we had 80.27 g and after second we had 80.29 g. We did not do a third heating because your two masses after heating should only vary .02 if it differs any more than you have to do the third heating. Once you have all your data, you can be calculating the percentage but you first must find the mass of water. To find the mass of the water you subtract the initial mass from the end mass, in my case our initial mass was 81.03 and our ending mass was 80.27, that would conclude that our mass of water was 0.74 g. To find the overall percentage you would take .74 and divide it by 2.02 (which was the amount of compound we used) then multiply it by 100, and we got 37%. If you used 6.0 g of hydrate that percentage would still be the same because the 37% should be a constant that can be used to show how much of any mass of the hydrate you use is water alone and 6.0 g would leave you with around 2.2 g of water. The results are reliable because I followed the rules of using significant digits and because we didn’t lose any of the hydrate, which would’ve messed up our calculations. For example, if we had blown, shaken or spilled the hydrate out of the the evaporating dish we were boiling the hydrate in, then some of the hydrate would’ve fallen out and now the amount would be lower than what it should’ve been.
CuSO4 * 5H2O Total mass of hydrate is 249.6 g because Sulfur is 32.07 g, Copper is 63.50 g O4 is 64.00 g, H2O is 18.00 g and you have 5, which means there’s 90.00 g H2O.
Percent Error: Actual-theoretical/theoretical*100 (AT&T)
% error= .74-.728/.728*100=1.65%
Percent composition of Hydrate:
Mass water/Mass hydrate * 100 = Percent composition of hydrate
90.00 g H2O/249.60 g CuSO4*100 = 36.05% H2O