How to Write a Conclusion Part of a Chemistry Lab Report

A student drafting a conclusion part of a chemistry lab report 


This part is the end of the climax of your chemistry lab report. Strive to write it in an ending tone. So, what are the requisites in the conclusion of a chemistry lab report? When writing an excellent lab report students must include the restatement of the experimental objectives, summary of the experiment and recommendation for the future experiment. Though, some conclusion lacks recommendation for the future study. Therefore, students should adhere to the provided instructions.

I will use conclusion parts of previous chemistry lab reports (lab reports discussed in previous lessons) as examples.

Example 1
Restatement of the experimental objectives
The experiment investigated the values of pKa, pKb and the concentration of a weak base (aqueous ammonia) and a weak acid (acetic acid) using the titration curves.

Summary of the experiment
The determined pKa value of acetic acid was less than the accepted pKa value of acetic acid (4.7). Surprisingly, the experimental Ka value (5.012 X 10-5) of acetic acid was greater than the expected Ka value of acetic acid (1.08 X 10-5). On the other hand, the experimental pKb value (9.57) of aqueous ammonia was greater than the accepted pKb value (4.75). Moreover, the experimental Kb value (2.692 X 10-10) of aqueous ammonia was greater than the accepted Kb value of aqueous ammonia (1.76 X 10-5). The comparison of percentage errors between pKa and Ka of acetic acid indicated that pKa of acetic acid had smaller percentage error as compared to Ka of acetic acid. Additionally, percentage error comparison between pKb and Kb of aqueous ammonia pointed out that pKb of aqueous ammonia had smaller percentage error than the percentage error of its Kb values.  Kb values of aqueous ammonia recorded the highest percentage error. Percentage error of Kb values of aqueous ammonia was greater than 100%. 

Contaminated apparatus and chemicals used might have negatively affected the accuracy and precision of the experimental results, thus resulting in percentage errors. The evaluation between monitoring titration of sodium hydroxide-acetic acid and monitoring titration of aqueous ammonia-hydrochloric acid shows sodium hydroxide-acetic acid titration was helpful than aqueous ammonia-hydrochloric acid since it had few experimental errors.

Example 2
Restatement of the experimental objectives
The experiment helps the students to understand different functional groups of organic compounds. Moreover, it enables learners to appreciate the use of IR spectroscopy in the determination of structures of organic compounds.

Summary of the experiment
From Figure 1, Figure 2, and Table 1 the unknown organic solution #1 was 2-pentanone while the unknown solution #2 was ethyl benzoate. The experimental results were confirmed by the peak values for C=O stretch and C-O stretch for aliphatic ketones and unsaturated esters in literature. The contaminated apparatus and chemicals used might have affected the validity of the experimental results.

Final remarks
In both examples, the experimental future recommendations are not provided. This happened because the experimental instructions did not require experimental future recommendations.  Therefore, students should write their chemistry lab report according to the institutions’ guidelines. I have used subtitles (restatement of the experiment and summary of the experiment) to show you where you should include them. However, your restatement of the experimental objectives and summary of the experiment should be within the body of your conclusion without using subtitles as I have used.
Kindly check previous lessons here. If you have a question regarding writing a conclusion of a chemistry lab report then comment below.

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