- Date EXPERIMENT EQUILIBRIA: LE CHATELIER\'S PRINCIPLE she Explanatio Equilibri
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- Date EXPERIMENT EQUILIBRIA: LE CHATELIER'S PRINCIPLE she Explanatio Equilibrium Observation A. Chromate Equilibrium Addition of 2 ml of 0.1 M Nellow in coior potassium dichromate solution in a test tube Addition of 2 ml of M turned orange sulfuric acid to the dichromaten colo leh turned orange solution Addition of a few dros of 1 M oter or a Became a ier orange Addition of a few drops of 1 M I Ad u er or a B. Dissociation of Acetic Acid Cleartvineddrk sodium hydroxide Addition of 3 drops of methylt IYSt orange indicator followed by addition of sodium acetate to pink became 1+ Was the test tubeg organg ka?par kpine Addition of methyl orange followed by addition of 1 M in orance. fllwed by ditio oMrance. NaOH solution C. Dissolution of Ammonium Chloride Dropwise addition of Secame erystaized concentrated HCI Heat the test tube above with VIiSolved cr Sa NH,Cl and HC Addition of water to EQUILIBRIA.Explanation / Answer
Le chatlier’s principle,if the mass on reactant side increases, the equilibrium shifts in the forward direction and the reverse happens when mass of product increases
1) The equilibrium between chromate and dichromate exists in aqueous solution,
2 CrO42 + 2 H+ Cr2O72 + H2O
In acidic medium dichromate ion(orange) is predominant,while in alkaline medium chromate ion (yellow) is predominant.
When acid added equilibrium shifts forward, dichromate is formed.
2) Methyl orange is a pH indicator with equilibrium existing between its different forms in acidic and basic and neutral medium.
In basic, methyl orange moves from red to orange and finally to yellow with the reverse occurring in acidic medium.
Methyl orange (pH indicator)
below pH 3.1 (red) above pH 4.4(yellow)
NaOH is strongly basic,also sodium acetate is weakly basic.Equilibrium shifts forward.
3)Dissolution of NH4Cl(s)
NH4Cl(s)NH4+(aq) + Cl-(aq)
When HCl added, the equilibrium shifts towards left ,crystallization of salt occurs , NH4Cl(s) precipitated
When heated equilibrium shifts forward, salt dissolves
Addition of water,more ions are formed, energy used up in breaking ions apart=endothermic
4)CuSO4 complex
The copper ion in solution as [Cu(H2O)6]2+ imparts a characteristic pale blue color to the solution. ammonia is a weak base dissociates to give hydroxide ion
NH3(aq) + H2O(l) NH4+(aq) + OH-(aq) pKb = 9.25
The hydroxide ion reacts with the complex hexaaquacopper(II) ion to form the insoluble compound, copper(II) hydroxide dihydrate as follows=
[Cu(H2O)6]2+(aq) + 2 OH-(aq) [Cu(OH)2] * 2 H2O(s) + 2 H2O(l)
Which reacts with ammonium hydroxide to give,
Cu(OH)2 + 4NH4OH Cu(NH3)4(2+) + 4H2O + 2OH-
a tetraamminecopper(II) complex (dark blue) is highly soluble in water . The precipitate of Cu(OH)2 dissolves because the formation constant for the complex is very high and drives Cu(OH)2 <--> Cu2+ + 2OH- to the right of the equilibrium.
HCl addition shifts the equilibrium to the left for dissociation of ammonium hydroxide.
5) Cobalt complex
Hexaaquacobalt(II) complex=pink +HCl=tetrachlorocuprate(II) +H2O
[Co(H2O)6]2+ (pink)+4Cl-[CoCl4]2- (blue) +6H2O
CoCl2+6H2O [Co(H2O)6]2+
Adding water shifts the equilibrium to the left,while adding CoCl2 shifts the equilibrium to the right.
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