Chem 534                                                                                           Name_____________

Lab 3.1            Qualitative Aspects of Chemical Equilibrium           In equil’m with____


Purpose:          to see how the following equilibrium can be disturbed with KSCN, Fe(NO3)3(aq), and Na2HPO4(aq


                        Fe+3(aq) +          SCN-1(aq)              = FeSCN+2(aq)

                        Yellow                         colourless                     red


Equipment:     petri dish, graduated cylinder, 100 ml beaker, white paper

Chemicals:      0.0020M KSCN, Fe(NO3)3(aq), solid KSCN, Na2HPO4(aq), water




1.         Add about 25 mL ( use graduated cylinder) of 0.0020M KSCN ( potassium thiocyanate) solution in to a beaker. Add 25 mL of water. Note the colour in your data table.


2.         Note the colour of Fe(NO3)3(aq) in your data table.


3.         Next record the colour of KNO3(aq).


4.         At this point you should realize which ion is responsible for the colour of Fe(NO3)3(aq) and of  SCN-1(aq).


5.         Add 5 drops of Fe(NO3)3(aq)  ( a source of Fe+3), and wait for equilibrium to reestablish itself. 


            (You have just created the equilibrium described by the equation in the "purpose" by making FeSCN+2(aq) )


             Record the new colour in your data table.


6.         Pour equal amounts of the solution from the beaker into four numbered petri dishes on white paper. Leave petri dish 1 alone . (This will act as a reference solution so that you remember the original colour of the undisturbed equilibrium mixture.)


7.         To petri dish 2, add two crystals of solid KSCN, and record your observations.


8.         To dish 3, add three drops of  Fe(NO3)3(aq), and record your observations.


9.         To dish 4, add 6 crystals of Na2HPO4. What happens? Record your observations.



















Fe+3(aq) + SCN-1(aq) = FeSCN+2(aq)



Adding solid KSCN to above equilibrium



Adding Fe(NO3)3(aq) to above equilibrium



Adding Na2HPO4(aq) to above equilibrium






In steps 7, 8 and 9, you disturbed the equilibrium on three separate occasions. Explain your observations by mentioning what is going on at the molecular level.


Adding solid KSCN to above equilibrium








Adding Fe(NO3)3(aq) to above equilibrium






Adding Na2HPO4(aq)  to above equilibrium








Conclusion:     In three sentences (no more, no less), summarize the effect of the 3 chemicals used to disturb the equilibrium(include equation) in the purpose