Tetraamminecopper(II) sulphate hydrate
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Tetraamminecopper(II) sulphate hydrate Write-up Purpose The purpose of this experiment is to form tetraamminecopper(II) sulphate hydrate and determine the yield. Materials CuSo4·5H2O NH3 (concentrated) Ethanol 50 cm3 measuring cylinder 250 cm3 beaker Spatula Equipment for vacuum filtration Procedure Weigh out approximately 5.0g of CuSo4·5H2O Dissolve it in 30 cm3 water in the beaker Add 10 cm3 concentrated ammonia (NH3) and stir the solution Add 40 cm3 ethanol and stir carefully for a couple of minutes. Filter the solution through equipment for vacuum filtration. Transfer the product to a clean weighing boat and leave to dry. Procedure and observations in class First 5.01g of CuSo4·5H2O was weighed out.
Mr = 64 + 32 + (16 x 4) + (5 x 16) = 250 m = 5.01 n = 5.01 / 250 = 0.02004 0.0200 moles (3 s.f.) 2. "Concentrated ammonia contains 25% NH3 by mass. The density of concentrated ammonia is 0.91g/cm3 . Calculate the number of moles of NH3 ." Density of con. ammonia = 0.91g/cm3 and in the procedure there was used 10 cm3, so therefore mass of ammonia used: 0.91 x 10 = 9.1g Since only 25% of ammonia is NH3 , mass of NH3 : 9.1 x 0.25 = 2.275g From here the amount of moles can be calculated by the formula n = m / Mr.
5H2O and Cu(NH3)4SO4 . H2O is 1 : 1. Therefore 0.02 moles of CuSO4 . 5H2O will give 0.02 moles of Cu(NH3)4SO4 . H2O. By using the formula m = Mr x n the theoretical yield can be calculated: n = 0.02 Mr = 246 m = 0.02 x 246 = 4.92 g "Calculate the yield in percentage of the theoretical and comment on any difference." The yield in percentage can be calculated by the "formula": actual mass / expected mass. 4.82 / 4.92 97.9% (3 s.f) Because the difference is so small (2.1%) the experiment can be considered successful. The difference could have been caused by different things like: a small measurement mistake, a little bit was spilt or not transferred when the solution was held in the Buchner flask.
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