Chem
Unit 2 PPA 1
Complexometric Determination of Nickel using EDTA
Introduction:
The Aim of the experiment is to determine the percentage of nickel salt using a complexometric technique.
Ethylenediaminetetraacetic acid (EDTA) is a hexadentate ligand which forms stable complexes with most metal ions, thus is widely used to determine metals in complexometric titrations. EDTA can be represented as H4Y and in alkaline conditions, it exists as Y+ ions:
The Y4- ions form 1:1 complexes with metal ions. For example, Ni2+ ions bind with them to form a stable octahedral complex NiY2-.
An ordinary indicator cannot be used since the reaction does not involve a simple acid – alkali neutralisation so the end point of an EDTA complexometric titration can be detected by means of a metal ion indicator (an organic dye which changes colour when it binds with metal ions.) For it to be suitable in an EDTA titration, the indicator must bind less strongly with the metal ions than does EDTA.
Procedure:
Firstly, the theoretical percentage by mass of nickel in NiSO46H20 was calculated. Approximately 2.6g of hydrated nickel(II) sulphate was transferred to a weighing bottle and both the contents and bottle were weighed. About 25cm3 of deionised water was added to a 100cm3 beaker and the bulk of the nickel salt was transferred to the water. The weighing bottle was then reweighed with the remaining salt. The solution in the bottle was stirred until the solid dissolved and the solution was then transferred to a 100cm3 standard flask. The beaker was then rinsed with deionised water and the rinsings were added to the standard flask. This procedure was repeated until the solution reached within a centimetre of the graduation mark on the standard flask. Using a dropper, the solution was made up to the graduation mark with deionised water. The flask was stoppered and inverted several times to ensure the contents were thoroughly mixed. The burette was then rinsed with 0.10mol l-1 EDTA and
Complexometric Determination of Nickel using EDTA
Introduction:
The Aim of the experiment is to determine the percentage of nickel salt using a complexometric technique.
Ethylenediaminetetraacetic acid (EDTA) is a hexadentate ligand which forms stable complexes with most metal ions, thus is widely used to determine metals in complexometric titrations. EDTA can be represented as H4Y and in alkaline conditions, it exists as Y+ ions:
The Y4- ions form 1:1 complexes with metal ions. For example, Ni2+ ions bind with them to form a stable octahedral complex NiY2-.
An ordinary indicator cannot be used since the reaction does not involve a simple acid – alkali neutralisation so the end point of an EDTA complexometric titration can be detected by means of a metal ion indicator (an organic dye which changes colour when it binds with metal ions.) For it to be suitable in an EDTA titration, the indicator must bind less strongly with the metal ions than does EDTA.
Procedure:
Firstly, the theoretical percentage by mass of nickel in NiSO46H20 was calculated. Approximately 2.6g of hydrated nickel(II) sulphate was transferred to a weighing bottle and both the contents and bottle were weighed. About 25cm3 of deionised water was added to a 100cm3 beaker and the bulk of the nickel salt was transferred to the water. The weighing bottle was then reweighed with the remaining salt. The solution in the bottle was stirred until the solid dissolved and the solution was then transferred to a 100cm3 standard flask. The beaker was then rinsed with deionised water and the rinsings were added to the standard flask. This procedure was repeated until the solution reached within a centimetre of the graduation mark on the standard flask. Using a dropper, the solution was made up to the graduation mark with deionised water. The flask was stoppered and inverted several times to ensure the contents were thoroughly mixed. The burette was then rinsed with 0.10mol l-1 EDTA and