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

 

Procedure:

 

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.

 

 

 

Data:

 

STEP

ACTION

COLOUR OBSERVED

1

KSCN(aq)

 

2

Fe(NO3)3(aq)

 

3

KNO3(aq)

 

5.

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

 

7.

Adding solid KSCN to above equilibrium

 

8.

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

 

9.

Adding Na2HPO4(aq) to above equilibrium

 

 

 

Analysis:

 

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