instructions:
The discussion should be at most 2 pages, double spaced, 10-12 point font. the discussion should contain
at least 3 paragraphs, one for each of the experimental parts, and one additional paragraph which either explains what you will be writing, which summarizes what you wrote or which ties the 3 parts of the experiment together. The discussion for each part of the experiment should focus on explaining the results,
interpreting the results and discussing whether they are reasonable (remember to use context for example,
literature values for any results you have calculated). Observations should be used to interpret what is happening
chemically. (For example, instead of stating, The colour of the solution changed (an observation), it is better to
explain by stating, Addition of Fe(NO3)3 to KSCN, a clear and colourless solution, resulted in an orange coloured
solution due to the formation of the iron complex FeSCN2+.) When writing your discussion, you should consider
the following questions and make sure that your answer is incorporated into your discussion seamlessly (in other
words, please do not number your responses or put them in separate paragraphs).
1. Go through the steps that were performed by you in the lab procedure.
2. Carefully note what chemicals were added to the test tube at every step.
3. Write a reaction for what was happening in the test tube.
4. In Step 1 of the tetrachlorocobaltate(II) ion reaction, there is a warning that all glassware must be dry when preparing the equilibrium solution. Explain why this warning was included.
5. For test tubes 2 through 6, in each part of the experiment, explain how each change affected the equilibrium in terms of how each change affected the value of Q or K and how this is consistent with your
observation.
6. For Tubes 2, 3 and 4 include in your analysis what happens chemically when each reagent is added.
State the direction in which the equilibrium shifts and relate how the change in solution color supports
your conclusions.
7. Explain your observations using the chemical activities and the concepts of equilibrium. How did heating and cooling the test tube affect the equilibrium? What does this tell you about the reaction? Explain
using heat as a reactant or product in your reaction.
8. In Step 8 of the iron thiocyanate experiment, you add NaF to the test tube. Why do you add it and what
is its purpose? Write the balanced net ionic equation for the reaction of Fe3+ and NaF. Explain, in your
own words, how this second reaction affects the equilibrium of the iron thiocyanate reaction and what
this indicates about the stability of the iron(III) fluoride complex compared to the iron(III) thiocyanate
complex.
9. Write the balanced net ionic equation for the reaction of Cl
and AgNO3
. Explain, in your own words,
how this second reaction affects the equilibrium of the tetrachlorocobaltate(II) ion reaction. Be sure to
mention what specific property of the product drives this shift in equilibrium.What do the observations
lead you to conclude?
10. How do these observations relate to your reactions in particular?
11. Briefly (2 sentences maximum) explain what a buffer is and how it functions. What have you been able
to accomplish in the buffers part of the experiment.
12. How are your observations related to the experiment being performed? How close are the calculated
and measured pH values for the different buffer solutions?
13. Explain the terms being used in the experiment specifically with respect to your results (ie. Buffer
capacity). Describe any patterns observed between buffer capacities and the concentration of acid or
base in each buffer solution.
14. What can you conclude about buffers and your buffers in particular?
15. At every step possible, use chemical equations and the concepts of equilibria to explain anything you
write.
