Introduction:The Aim of the experiment is to find the per centum of Ni salt utilizing a complexometric technique. Ethylenediaminetetraacetic acid ( EDTA ) is a hexadentate ligand which forms stable composites with most metal ions. therefore is widely used to find metals in complexometric titrations. EDTA can be represented as H4Y and in alkalic conditions. it exists as Y+ ions:
The Y4- ions form 1:1 composites with metal ions. For illustration. Ni2+ ions bind with them to organize a stable octahedral complex NiY2- .
An ordinary index can non be used since the reaction does non affect a simple acid – base neutralization so the terminal point of an EDTA complexometric titration can be detected by agencies of a metal ion index ( an organic dye which changes coloring material when it binds with metal ions. ) For it to be suited in an EDTA titration. the index must adhere less strongly with the metal ions than does EDTA. Procedure:
First. the theoretical per centum by mass of Ni in NiSO46H20 was calculated.
Approximately 2. 6g of hydrated Ni ( II ) sulfate was transferred to a weighing bottle and both the contents and bottle were weighed. About 25cm3 of deionised H2O was added to a 100cm3 beaker and the majority of the Ni salt was transferred to the H2O. The weighing bottle was so reweighed with the staying salt. The solution in the bottle was stirred until the solid dissolved and the solution was so transferred to a 100cm3 standard flask. The beaker was so rinsed with deionised H2O and the rinses were added to the standard flask. This process was repeated until the solution reached within a centimeter of the graduation grade on the standard flask. Using a dropper. the solution was made up to the graduation grade with deionised H2O. The flask was stoppered and inverted several times to guarantee the contents were exhaustively assorted.
The burette was so rinsed with 0. 10mol l-1 EDTA and filled with the same solution. The pipette was rinsed with a small of the Ni salt solution and 20cm3 of this was pipetted into a conelike flask. The solution was so diluted to about 100cm3 with deionised H2O. Approximately 0. 05g of murexide index was added to the diluted Ni salt solution together with about 10cm3 of ammonium chloride solution. The mixture was so titrated with the EDTA solution and after the add-on of about 15cm3 EDTA solution. the solution was made alkaline by the add-on of about 10cm3 of 0. 88 aqueous ammonium hydroxide.
The titration was so continued to the end-point which was shown by the first visual aspect of a bluish-violet coloring material. This titration was used as a test tally. as sensing of the terminal point is really hard. The titrated solution was kept to assist observe the end-points in the subsequent titrations. The titration was repeated until two accordant consequences were obtained. The per centum by mass of Ni in the sample of hydrous Ni ( II ) sulfate was calculated utilizing the accurate concentration of the EDTA solution. For one finding. the per centum mistake was calculated and so the absolute mistake in the per centum of Ni in NiSO4 6H2O.
Consequences:Theoretical Calculation:GFM of hydrated Ni ( II ) sulfate. NiSO4. 6H2O = 262. 8X 100 = 22. 3 %% Ni = 58. 7262. 8
Experimental Consequences:Mass of hydrated Ni ( II ) sulfate used = 2. 6g| Rough titre| First titre| Second titre|Initial burette reading ( cm3 ) | 0| 19. 5| 0|Final burette reading ( cm3 ) | 19. 5| 40. 8| 21. 5|Volume of EDTA added ( cm3 ) | 19. 5| 21. 3| 21. 5|
Average of accordant consequences:= 21. 4 cm321. 3 + 21. 52Concentration of EDTA solution = 0. 10mol l-1
The figure of moles of EDTA used to respond with 20cm3 of Ni ( II ) solution =V x C= 0. 0214 ten 0. 10 = 0. 00214 molesTherefore. figure of moles of Ni2+ ions in 20cm3= 0. 00214 molesNumber of Ni2+ ions in the entire volume of 100cm3=0. 00214 ten 5 = 0. 0107 moles
Therefore. mass of Ni in salt= N x Fm= 0. 0107 ten 58. 7= 0. 62809gX 100From these consequences the % mass of Ni in the salt
= 0. 628092. 6= 24. 2 %
Decision:The per centum by mass of Ni in hydrous Ni ( II ) sulfate was shown by experiment to be 24. 2 % . This compares really good with the theoretical value of 22. 3 % .
Evaluation:The experimental consequence tantrums in really good with the theoretical consequence. This suggests that the hydrated Ni ( II ) sulfate used was really pure. Impurities such as other metal ions would hold reacted with EDTA to give higher titer values and. hence. a higher experimental value for the per centum of nickel present. During the first titration. it was rather hard to find when the end-point had been reached. but the visual aspect of the bluish-violet coloring material was crisp. The ammonia-ammonium chloride solutions are used as a buffer to maintain the pH invariable. Possible uncertainness values in the measurings include:
* Burette readings ±0. 05 cm3* Pipette volumes ± 0. 06 cm3* Balance readings ± 0. 01g ( ±0. 02g for tared mass )* Volumetric flasks ± 0. 2 cm3* The concentration of the EDTA solution.
Uncertainty in mass of NiSO4. 6H2O= 0. 02gX 100 = 0. 77 %% uncertainness in mass of NiSO4. 6H2O= 0. 022. 6
Uncertainty in volume of NiSO4 ( aq )= 0. 2cm3X 100 = 0. 20 %% uncertainness in volume of NiSO4 ( aq )= 0. 2100
Uncertainty in pipetted volume of NiSO4 ( aq )= 0. 06 cm3X 100 = 0. 3 %% uncertainness in pipetted volume of NiSO4 ( aq )= 0. 0620
Uncertainty in concentration of EDTA = 0. 0002mol l-1X 100 = 0. 2 %% uncertainness in concentration of EDTA= 0. 00020. 1
Uncertainty in titre volume of EDTA = 0. 1cm3X 100 = 0. 5 %% uncertainness in titre volume of EDTA= 0. 121. 4
% uncertainness in per centum of Ni= 0. 77 + 0. 2 + 0. 3 + 0. 2 + 0. 5= 1. 97 %
X 24. 2 = 0. 48 %Absolute uncertainness in per centum of Ni= 1. 97100
Hence. per centum of Ni in NiSO4. 6H2O= 24. 2±0. 5 %
Cite this Complexometric Determination of Nickel using EDTA Sample
Complexometric Determination of Nickel using EDTA Sample. (2017, Sep 26). Retrieved from https://graduateway.com/complexometric-determination-of-nickel-using-edta-essay-sample-essay/