CHM1011 - Chemistry I - S1 2025
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A student ended the experiment with 0.1400g of copper, having started with 0.2892g of CuCl2.2H2O.
Calculate the %yield of copper produced, i.e. the percentage recovery of copper compared to the expected amount.
(Hint: The reagents used are always in excess to the copper species (sodium hydroxide, sulfuric acid, and zinc). Hence, the copper species is always the limiting reagent. This means that the nCu=nCuCl2.2H2O at 100% yield.)
(Hint 2: If the copper produced was not adequately dried before weighing, then we may end up calculating a yield of >100%! Why is this?)
A student ended the experiment with 0.1400g of copper, having started with 0.2892g of CuCl2.2H2O.
Calculate the moles of pure copper (Cu) produced:
Calculations
Based on the experimental data provided, complete the following calculations.
A student ended the experiment with 0.1400g of copper, having started with 0.2892g of CuCl2.2H2O.
Calculate the moles of CuCl2.2H2O used:
Results
Experimental Data
Mass CuCl2.2H2O (g) | g |
|---|---|
Mass of Cu in CuCl2.2H2O (g) | g |
Mass of Copper recovered (g) | g |
% yield of Copper | % |
Observations
Type up a summary of your observations for each section.
- Section 2.1 (i) - Dissolution of Copper(II) chloride dihydrate:
- Section 2.1 (ii) - Copper(II) chloride to copper(II) hydroxide:
- Section 2.2 - Copper(II) hydroxide to copper(II) oxide:
- Section 2.3 - Copper(II) oxide to copper(II) sulfate:
- Section 2.4 - Copper(II) sulfate solution to copper:
Conclusion
The conclusion should answer the aim, and should state the (numerical) results. Think of it as a spoiler for the whole lab report!
For example:
If the aim was: To perform an accurate dilution of a food dye stock solution using a burette and a 25.00 mL volumetric flask, and to assess the accuracy of the dilution using UV-visible spectrophotometry.
Then the conclusion could be: A green food dye stock solution (22.0 ppm) was diluted by a factor of 5 to produce a 4.40 ppm solution. The accuracy of the dilution was assessed using UV-visible spectrophotometry (at 630 nm) and the %error of the dilution was determined to be 4.5%.
Discussion
This is where you discuss and give meaning to the results. You should also detail any experimental errors and make any other relevant comments about the experiment. Include possible improvements. Ensure you are not re-stating the method.
Discussion points to consider: (Note: The points below are not intended as questions! They are here to give guidance on what to include in your discussion. Do not simply list answers - incorporate them into a full discussion.)
- Relate results back to the aim and introduction of the experiment – what was trying to be done, did the results support the aim of the experiment?
- Discuss the yield. Are there alternative reaction pathways which could improve the expected yields? What are they?
- Discuss the chemistry behind the colour changes, and relate this to the actual transformations of copper throughout the experiment.
- What factors may have affected the final result? What are some sources of error that may have been encountered, and how would they have impacted on the results?
- If you actually wanted to achieve copper at the end (for example, if you had an ore that you were extracting), would this be a suitable method? Why/why not?
Discussion marking rubric:
| 0 | 1 | 2 |
Relates results to aims. | Interpretation of results not related back to original experimental aims. | Results partially related back to original experimental aims. | Key results interpreted in relation to experimental aims. |
Discussion and interpretation of results. | No interpretation or comparison of results is made. No discussion points are addressed. | Some interpretation or comparison of results is made. Some discussion points are addressed. | Key findings are summarised. Results are interpreted. Results are compared to expected/predicted values. All discussion points are addressed. |
Actual data used to validate statements. | No experimental data used to justify scientific statements/claims. Multiple scientific errors are present. | Some experimental data used to justify scientific statements/claims. Some scientific errors are present. | Experimental data used to justify all scientific statements/claims. The science is correct. |
Factors affecting results discussed. | No errors were raised or were only non-scientific/experimental errors raised. | Only some errors raised or several non-scientific/experimental errors were raised. The impact of the errors was not discussed. | Multiple errors/factors are raised and are scientific/experimental in nature (i.e. NOT human error). The impact of the errors was discussed. |
Writing Style | Many grammatical/spelling/scientific writing errors were noted, and/or discussion was over 330 words in length. | Some grammatical/spelling/scientific writing errors were noted. | The discussion was free of grammatical and spelling errors, was written in the past tense, used full sentences and a passive voice, and was within 300 words. |
Word limit: 300 words (+/- 10 %)
For guidance on writing a meaningful discussion, please refer to the following resources:
- SoC: Undergraduate Student Handbook
- RLO: Writing a Science Lab Report
- RLO: Writing for Assignments
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