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Writing A Good Lab Report

At every stage of an experiment, the accurate and unbiased recording of results is essential. Your lab report should be neat and legible and only written in pen or ink (blue or black ONLY). Do NOT use pencil or white-out!

Preparation of the pre-lab prior to carrying out the experiment helps to familiarize you with the objectives of the experiment and any hazards associated with that lab. The pre-lab usually includes an objective, references, answers to pre-lab questions, table of reagents and an experimental plan. You are expected to complete the pre-lab BEFORE you come to the lab and be adequately prepared for carrying out the experiment. The pre-lab is collected every lab period before the experiment starts. If you do not complete a pre-lab, you will NOT be allowed to start the experiment and you will receive a score of zero!

Use 1 or 2 complete sentences only and state the purpose or goal of the experiment you are about to carry out e.g. The objective of this experiment is to determine the identity of Compound A using functional group tests and to confirm its structure by using infrared and NMR spectroscopy.    

Reaction Scheme
If appropriate, draw a reaction scheme showing the starting materials, reagents and the expected product(s).   

Table of Reagents
This is a list of all the compounds that you will encounter during a particular experiment. Where applicable, you should include molecular weights, melting or boiling points and hazardous properties. This will help familiarize you with potential hazards of the experiment.

Experimental Plan
In order to help make your time in the lab more efficient, you are required to formulate a flow chart to summarize the key points of your experiment. By doing this, you should not need to keep referring back to your lab manual.

You are required to state the origin of all your resource/ reference material. List your references in the following order: author, book/ journal name, year, and page numbers. Note: Wikipedia is NOT a proper scientific reference!    


1. Wan, H., Organic Chemistry Experiments 261, Fall 2010, pg. 32-34.

2. Organic Chemistry Laboratory Website, Distillation Video.

3. Pavia, D. L. et al.; Introduction to Spectroscopy, Brooks/ Cole, 2009, 345-360.

4. Aldrich Online Catalogue: http://www.sigmaaldrich.com/canada-english.html    

Pre-lab Questions
Most labs will have pre-lab questions that you need to answer based on the procedures or the experimental. These questions serve to focus your attention on the main concepts of the experiment.

Results Table, Data, Observations, Calculations, and Products
Record all observations as your experiment progresses. It is important to note any changes in the experimental plan as well. You should record observations such as color changes, appearance of crystals, temperature of reactions, test results, physical properties obtained, as well as mass of reagents and products used. Your discussion and conclusion sections will be based on what you write in the observation section. 

You MUST write your observations and results directly in your lab report book. Do NOT record your observations on loose paper and then transfer it over to your report book. If you do this, you will have marks deducted from your final lab mark!

You should provide enough procedural information so that you can perform the experiment without any further external information or referring back to the lab manual. You should make enough observations to allow you to complete the objective stated in your pre-lab.

Accurately and neatly record your observations immediately after you observe them. If you delay recording an observation, you may forget later which could lead to difficulty writing up your discussion and conclusion sections.

Summarize your results in the results table. Do not forget to include your calculations such as yields. Only report what you observe. Do NOT record what you expect to observe! Remember to use the correct units and significant numbers when recording data.

If data needs to be recorded graphically, ensure that: 1) a uniform scale is used, 2) you use the whole graph paper, 3) the graph has a title and 4) both the x- and y-axis are labeled. Remember to include the units of measure and plot the dependent variable on the y-axis and the independent variable on the x-axis. Be sure to ascertain what type of graph is required e.g. a curve or a best-fit linear line.

Plot ALL graphs manually. Any computer-generated graphs will NOT be marked!

Discussion and Conclusion
Using complete sentences, you need to discuss the following:
  • What did or did not occur
  • What did or did not support the objective
  • Justify structures for unknowns (if necessary) 
  • Discuss TLC plates, Rf values, m.p. data and spectral (IR and/ or NMR) data
  • Comment on purity and yield    
You need to convince the reader (your TA) that your procedure and observations are valid. When writing your discussion, avoid the use of first person pronouns e.g. I or we. In the discussion, you are correlating all your results and showing how they relate to your objective. Do NOT just re-state your observations.

The conclusion should just be a few sentences that relate to whether or not you met your objective.

Include reaction mechanisms where applicable.

Spectral Data
Remember to attach any spectroscopic data (IR or NMR) that you obtained during the lab class. If you do not attach this data, the discussion in the report is meaningless and you will likely receive no marks!