The first experiment aimed to cipher the accurate value of H2O of hydration ( ten ) in hydrated Cu ( II ) sulfate.
The 2nd experiment aimed to detect the behaviour of different ligands of Cu ( II ) .
The value of x hydrated crystals are common, Cu ( II ) sulfate is one: CuSO4: xH2O ( S ) . The value of ten can be calculated. We need to cognize the mass of CuSO4: xH2O ( M1 ) and the mass of CuSO4 ( M2 ) , therefore xH2O can be solved: m1- m2.X can be calculated by this manner: ( m1- M2 ) /18.
Copper ( II ) sulfate is anorthic crystals, which has three axes and the length is non equal to each other, has blue coloring materials and is crystalline. Anhydrous Cu ( II ) sulfate is grey white atoms, which are easy to fade out in H2O and be hygroscopic that means easy moist. ( Lister and Renshaw, 2000 ) . The equation is
CuSO4: xH2O ( S ) — & gt ; CuSO4 ( S ) + xH2O ( cubic decimeter )
Complex ions can place other electronic braces replace H2O molecules which surround the cation. Chemguide ( 2003 ) indicates compounds have colours because they absorb visible radiations, such as gamma beams, X raies, infra-red beams, wireless moving ridges, etc. It shows as figure 1 ( Chemguide 2003 ) .
Therefore, when the sunshine base on balls the Cu ( II ) sulfate solution, ruddy part of the spectrum is absorbed, therefore, hcopper ( II ) sulphate solution will look cyan, show as figure 2 ( Chemguide 2003 ) .
When surplus of ammonia solution was added, a color alteration from cyan to dark blue can be seen, figure 3 ( Chemguide 2003 ) . Harmonizing to Chemguide, The H2O wholly wraps up a Cu ion utilizing all 6 of the places that we have seen earlier. When surplus of ammonia solution was added, ammonia replaces 4 or 6 H2O molecules, the energy of the ions become larger, so that it can absorb xanthous part, which has higher energy than ruddy part. ( Chemguide 2003 )
Chemicals: bluish Cu ( II ) sulfate ( aq ) , concentrated hydrochloric acid, ammonia solution. Equipment: crucible, spatula, paper cartridge holder, burner, tongs, electronic balance, base, conelike flask and pipettes ( Lane, 2009 ) .
The first experiment follow these stairss. First, the interior of a melting pot was cleaned utilizing tissue. It was weighted on the electronic balance ; a paper cartridge holder was besides included in the mass. The weight of melting pot was made down. About 2g of Cu sulfate was placed, indoors and reweighted. Subsequently, the melting pot was placed on the base and for heating for approximately 5minutes. The hydrated crystals were stirred with the paper cartridge holder. The alteration of coloring material was observed carefully. After 5 proceedingss, the hot melting pot was removed by tongs into dessicator for chilling. When cool plenty to touch, the melting pot was weighted. The procedure was repeated ( Lane, 2009 ) .
The 2nd experiment follow these stairss. Initially, hydrated Cu ( II ) sulfate was put into three conelike flasks and 100cm3 H2O was added. Then the three conelike flasks were shaken, to fade out the solid.
Second, concentrated hydrochloric acid was added to one, and observed.
Third, some ammonia solution was dropped into a 2nd flask until the coloring materials alterations with shaking ( Lane, 2009 ) .
As can be seen from table 1, the value of H2O of crystallisation of Cu ( II ) sulfate can be calculated:
CuSO4: xH2O ( S ) — & gt ; CuSO4 ( S ) + xH2O
The mass of CuSO4: xH2O is 2.22g ; the mass of CuSO4 is 1.4g, besides the Mr of CuSO4: xH2O is 160+18x and the Mr of CuSO4 is 160. Lister provinces that Mr is the molecule mass, which compare with an atom of H ( Lister and Renshaw, 2009 ) . Therefore, xH2O can be solved 2.22g/ ( 160+18x ) =1.4g/160, the ten is 5.2, about CuSO4:5H2O ( S ) ? CuSO4 ( S ) + 5H2O ( cubic decimeter ) .
The mistake possibly comes from two sides: foremost, computation ; 2nd, the Cu ( II ) sulfate has non wholly change to anhydrous salt, Cu ( II ) sulfate may go on to absorb the H2O vapour in the air. Because of clip, the Cu ( II ) sulfate was merely heated twice. Repeat warming will do certain the reaction has finished. In add-on, the crucible must be cooled down before weighing. If overheating, the compound can turn black:
CuSO4 ( S ) — & gt ; CuO ( S ) +SO3 ( g ) ( Chemguide 2003 )
The CuO is black. Moverover, better following clip it should avoid hydrated Cu ( II ) sulfate being in the air excessively long and must rapidly set it into a dessicator. Repeat heating until the mass of anhydrous Cu ( II ) sulphate remain unchanged.
Part B experiment, it was noted that the Cu ( II ) sulphate solution and the concentrated hydrochloric acid solution reacted and the solution coloring material alteration to green. This can be explained as follows:[ Cu ( H2O ) 6 ] 2+ ( aq ) + 4Cl+ ( aq ) — & gt ; [ CuCl4 ] + ( aq ) + 6H2O ( cubic decimeter ) ( Chemguide 2003 ) .
That means six H2O molecules were replaced by four chloride ions, the coloring material alteration was reference in the reference the coloring material once more.
Furthermore, the ammonia solution reaction has a bluish green coloring material:[ Cu ( H2O ) 6 ] 2+ ( aq ) + 2NH3 ( cubic decimeter ) ? [ Cu ( H2O ) 4 ( OH ) 2 ] ( aq ) + 2NH 4+ ( aq ) ( Chemguide 2003 ) .
After more ammonium hydroxide is added the coloring material alteration to dark blue is consequence of [ Cu ( H2O ) 6 ] 2+ + 4NH3? [ Cu ( NH3 ) 4 ( H2O ) 2 ] 2+ + 4H2O ( Chemguide 2003 ) .
To summarize, the hydrous expression of CuSO4: xH2O ( S ) was calculated to be CuSO4:5H2O. The accurate value of ten in the equation for hydrate Cu ( II ) sulfate is similar to theory. And observe the different colorss of complex ions in solution, the coloring material alteration from bluish to green of Cl- ligands and from bluish to cyan so to dark blue of NH4- ions, demonstrate the procedure was clearly.
- Chemguide [ online ] ( 2003 ) Copper Available at: hypertext transfer protocol: //www.chemiguide.co.u/inorganic/transition/copper.html Adapted day of the month 2009.12.27
- Lane, R. ( 2009 ) Chemistry Practical 2 Handout
- Lister, T. and J. Renshaw ( 2000 ) . Chemistry for Advanced Level ( 3rd edition ) . Cheltenham: Nelson Thornes Ltd