12 a Expriment Essay

MATERIALS AND PROCEDURE As per Essential Experiments for Chemistry pages 163–170 RESULTS TABLE 1 Equilibrium involving bromocresol green Initial colour of bromocresol green in water = Reagent added HCl (step 3) more HCl (step 4) NaOH (step 5) more NaOH (step 6) Stress Colour change and # of drops required Direction of shift ver. 02/2012 1 Chemistry 12 Unit 2 Reaction Equilibrium

TABLE 2 Equilibrium involving iron(III) thiocyanate ion Colour of FeCl3 Solution = ______________________________ Colour of KSCN Solution = ______________________________ Colour of FeSCN complex = ___________________________ Reagent added KSCN (test tube B) FeCl3 (test tube C) KCl (test tube D) NaOH (test tube E) TABLE 3 Equilibrium involving cobalt(II) complexes Colour of CoCl4 solution = ___________________________ Colour of Co(H2O)6 solution = ________________________ Colour of CoCl2 + HCl Stress step 4 (water added) step 5 (heated step 6 (cooled) TABLE 4 Equilibrium involving chromate and dichromate ion 0. M K2CrO4 Steps 1,2,3 initial colour 1M NaOH added 1M HCl added 0. 1M K2CrO4 Step 4 initial colour 1M HCl added 1M NaOH added Steps 5&6 Steps 7&8 0. 1M K2Cr2O7 0. 1M K2CrO4 Step 9 Add 0. 1M Ba(NO3)2 0. 1M K2Cr2O7 0. 1M K2CrO4 Initial colour + 1M HCl + 0. 1M Ba(NO3)2 + 1M NaOH Initial colour + 1M NaOH + 0. 1M Ba(NO3)2 + 1M HCl 0. 1M K2Cr2O7 0. 1M K2Cr2O7 Colour of CoCl2 + H2O Colour observation Direction of shift 2+ 2+ 2+ Stress Colour observation Direction of shift Expt 12A Investigating chemical equilibrium. ocx 2 Chemistry 12 Unit 2 Reaction Equilibrium TABLE 5 Equilibrium involving copper (II) complexes 0. 1M CuSO4 Appearance ANALYSIS OF RESULTS 1. In Part 1, how would increasing the molarity of NaOH solution from 0. 1M to 0. 5M affect the number of drops required for the observed colour changes? __________________________________________________________________________________________ __________________________________________________________________________________________ 2.

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Apply Le Chatelier’s principle to explain the results obtained when 1M NaOH was introduced into the iron(III) thiocyanate ion equilibrium system. __________________________________________________________________________________________ __________________________________________________________________________________________ __________________________________________________________________________________________ 3. If the hydrated cobalt(II) ion complex were refrigerated, what would you predict as the colour of the refrigerated solution? Explain. _________________________________________________________________________________________ __________________________________________________________________________________________ __________________________________________________________________________________________ __________________________________________________________________________________________ 4. Look at the equilibrium equation for the reaction involving the hydrated cobalt(II) ion complex. From your lab results, which reaction (forward or reverse) is endothermic? Cite evidence for your answer.

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