Anyone want to critique a lab report (chemistry)?

[biochem850]

Homework Statement

I've not written a lab report since prep school and I need some critiques (thorough).

see attached

Homework Equations

The Attempt at a Solution

 

[JohnRC]

Purpose section: This reads a little as though it is copied straight from your instructions. It is certainly in very formal and stilted language -- might read more comfortably if you had the skill to write in precise but more natural language. Do you have clear instructions about what is expected in this part of your report (different teachers have different preferences about this sort of thing)?

Purpose line 4: Should be "phenomena" (plural of "phenomenon")

Procedure: Nowhere in the procedure section is there a mention of the pipette measurements that you discuss extensively in your discussion section. In steps 1 and 2 you have not specified whether or not the volume was cross-checked with any other measurement. Why was the erlenmeyer flask in section 2 filled beyond the calibration marks?

Discussion: "it was determined that the standard deviation of the volume of delivered water via the pipette was 9.8 ± 0.07-mL. ". This is not correct. The average volume of water delivered (not "delivered water") was 9.8 mL, with a standard deviation of ±0.07 mL.

Discussion: You really need to say somewhere -- preferably in procedure, but if not there, then in discussion -- how you measured accurate volumes of water delivered by pipette. This is all but impossible to do by a volume measurement; I presume that your weighed the aliquots by difference on an analytical balance? Did you assume that the density of your water was 1.000 kg/L or did you make a temperature correction for the density of water at the actual lab temperature? It is very important to include this in your discussion. The density of water at 25°C is in fact 0.997 kg/L, so it could make a small difference to your results. You also would get the best marks here if you were to hazard an opinion on whether your systematic error was a calibration error for your pipette or an operation error in use of the pipette by inexperienced operator. One possible check on this might have been to see if another student operator got the same systematic error with that particular pipette, or quite a different one.

Do you need to draw conclusions about precision, ease of use, reliability, and purpose of each of the instruments that you used in this exercise?

All of this is making a bit of a meal out of what was probably a rather simple exercise, but you did ask for a thorough critique, and the points I have made are those I would have been looking for if I were going to award an A+ type mark for this exercise.