Determination of nickel Essay

INTRODUCTIONEDTA (HY) is widely used to determine metals in complexometric (a volumetrical analysis where the formation of a coloured complex is used to indicate the end point of a titration) titrations as it forms stable complexes with most metal ions. EDTA is a tetracorboxylic acid and in alkaline conditions, it exists as Y ions, which form 11 complexes with metal ions like plate(II) ionsY + Ni NiYA metal ion exponent (an organic dye which changes colour when it harbours with metal ions) shows the end of an EDTA complexometric titration. However, for a metal ion indicator to be suitable in n EDTA titration, it must not bind as strongly with metal ions as EDTA does. Murexide is therefore suitable.AIMThe aim of this experiment is to determine the percentage of nickel in a nickel(II) sodium chloride utilise EDTA.Approximately 2.6g of hydrated nickel(II) sulphate was transferred to a weighing bottle and the contents weighed and about 25cm of deionised water was added to a 100cm be aker and the nickel transferred to the water. The bottle was weighed without any remaining season and then the mixture was stirred until the solid was dissolved before the resulting stem was transferred to a 100cm standard flask.The beaker was then rinsed several times with deionised water and the rinsings were added to the standard flask. The solution was filled up to the graduation mark with deionised water and the flask was stoppered and inverted several times to mix the contents.The burette was rinsed with 0.01moll EDTA and filled with the same solution. The 20cm pipette was rinsed with a little of the nickel salt solution and then 20cm of it was pipetted into a conical flask. The solution was diluted to about 100cm with deionised water and murexide indicator ( most 0.05g) was added to the diluted nickel salt solution along with appromimately 10cm of ammonium chloride solution.The mixture was titrated with the EDTA solution and after and after the addition of about 15cm the s olution was made alkaline by addingapproximately 10cm of 0.88 aqueous ammonia (concentrated ammonia solution). The titration was then continued to the end point, shown by the first appearance of a blue-violet colour. Titrations were repeated until two concordant results were obtained.RESULTSMass of 1 Mole of NiSO4.6H2O 262.8gMass of 1 Mole of Ni 58.7gTheoretical Percentage by MassVolumes of EDTA used in titration 1st 20.2cm32nd 20.9cm33rd 20.4cm3 medium 20.5cm3Moles of EDTA used = 0.1 x 0.0205 = 0.00205 MolesEDTA reacts with Nickel in a 11 ratio, so the number of moles of Nickel in 20cm3 of the salt solution = 0.00205MolesNumber of Moles in 100cm3 = 0.00205 x 5 = 0.01025 MolesNumber of Moles of Ni2+ in 2.6g of Nickel salt = 0.01025Weight of Ni2+ in salt = 0.01025 x 58.7 = 0.601675gCONCLUSION% Mass of Nickel in salt = 0.601675 2.60 = 23.14%