Lab Report

Introduction

Back titration is basically, an analytical technique in chemistry, which is performed mainstaywards in the method. That is, a user needs to find the concentration of a answerant of a given unknown concentration by reacting it with an free volume of another reactant of a known concentration. Once these mixtures react with each other, there will be a resulting mixture, which is titrated back in the process. The molarity of the excess, which was conducted in the process is taken down the stairs consideration too.

A squealer metal attempt is fade out(p) in nitric acid to produce Cu(II), and the oxides of nitrogen argon removed by appending H2SO4 and boiling to remove SO3 fumes. The solution is modify with ammonia and then slightly acidified with H3PO4 . The phosphoric acid in addition complexes any iron(iii) that might be present and prevents its reaction with I- . at long last , the solution is treated with excess KI to produce CuI and as equivalent amount of I3- , which is titrated with standard Na2S2O3 solution , using starch indicator . KSCN is added near the end point to displace adsorbed I2 o the CuI by forming a layer of CuSCN. For better accuracy, the Na2S2O3 is standardized against high-purity copper wire since some error occurs from reduction of copper(II) by thiocyanate.





Materials and Methods
Reagents:
The reagents apply in this experiment were 6M HNO3 , 3M H2SO4 , conc H3PO4 , 6M NH3 , KSCN , Starch indicator and 0.1M Na2S2O3 solution.
Methods:
Weight out three 0.20 to 0.25 g samples of pure copper foil and add to 250 ml flask. In a hood , dissolve in 10 ml 6 M HNO3 , heating on a water bath if necessary. Do in a fume hood.Add 10 ml conc.H2SO4 and evaporate to copious uncontaminating SO3 fumes..cool and add carefully 20 ml water. Boil 1 to 2 min and cool. Add 6 M NH3 dropwise with swirling of the sample solution until the first dark blue of the Cu(NH3)4 complex appears.Then add 3M H2SO4 until the blue color just disappears, followed by 2.0 mol conc H3PO4. assuredness to room...If you want to get a full essay, order it on our website: Orderessay



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