.
.
Heat.
Hydrated copper sulphate ---------- Water + Anhydrous .
Cu (ÉÉ) SO4 . 5H2O---------- 5(H20) + Cu (ÉÉ) SO4.
64 + 32 + (4 x 16) + 5(2 + 16) ---------- 5(2+16) + 64 + 32 + (4x16).
250 ---------- 90 + 160.
Through these calculations, we can work out that 250 grams of hydrated copper sulphate crystals give 90 grams of water and 160 grams of anhydrous sulphate. Now, we have to do the final stage of the calculation. We find out the percentage of water in hydrated copper sulphate crystals by dividing the mass of water by the mass of the hydrated copper sulphate crystals, and then multiply the answer by 100, to get a percentage.
90 x 100 .
250.
= 36%.
Results- Below are the results that I have obtained from the experiment that we did.
Experiment No 1 2 3.
Weight of crucible 24.77g 24.77g 24.77g.
Weight of crucible + crystals 25.77g 25.77g 25.77g.
Weight of crystals 1.0g 1.0g 1.0g.
Weight of crucible + crystals (after burning) 25.39g 25.41g 25.42g.
Weight of substance 25.39 - 24.77 = 0.62 25.41 - 24.77 = 0.64 25.42 - 24.77 = 0.65g.
Percentage water 38% 36% 35%.
Evaluation- I think that the results that we got are reliable for the conditions that the experiment was done under. All of the results that we got are very close to the predicted percentage that I made, with the exception of one, which was exactly the same. If more time had been allocated to do the experiment, I would have liked to complete a further two repeats, so that there was a better chance of getting good results.
I think that we could have made the experiment more accurate by doing it in more controlled conditions, for example in an isolated container, which we knew contained certain percentages of the gases in air. Also we could have timed the experiment, to make each result attained fairer. We could also have made sure that the temperature of the bunsen burner flame for each experiment was approximately the same.