parts of lab report

1 Handout Investigation : How Much Water is in the Hydrate ? Name: ________________________________ Group #: ___ Lab Date/Time: ____________ Directions: This worksheet will outline the information needed to write all of the sections in your first group report. As you work on the investigation, write data/results and/or observations to help with calculations in your notebook . Information included in your notebook will be used in the final exam. *The majority of the report is written in 3 rd person, past tense, passive voice, with no use of first person. *The report is to be double -spaced, written with proper grammar and spelling. Label each section. *A ttach Team Contribution Forms from each group member to your report (this is critical to ensure fair grades). *Attach individual section(s). This investigation requires you to complete the procedure section of the report, individually. The rest of the repo rt is a worksheet completed as a group. The group worksheet and individual sections are due 2 days after your lab! Due date _________time _______where ______________________________________________________. Introduction (1 point ): When chemical compounds incorporate water into their crystalline structure, they are called hydrates. Two salts were studied in t he course of this investigation. First , a hydrate with a known molar ratio of water to salt was studied: copper sulfate pentahydrate, CuSO 4 •5H 2O. By heating the hydrate, the water was driven off. After dehydrating the sample , the molar ratio of water to copper sulfate was determined . Next, an unknown hydrate was studied. A procedure was developed to determine the molar ratio of water to salt f or a p rovided unknown hydrate, (circle ) MgSO 4•XH 2O /FeSO 4•XH 2O. The percent by mass of water in the sample and the empirical formula of the hydrate were determined. Proce dure (2 point s):In this section, describe what your group did in both parts of the investigation in a paragraph format. Remember: **PAST TENSE!** (do not list/number procedures; use paragraphs). -When recording mass all numbers should be recorded and never rounded. -Include equipment, materials used , and concentration of any chemicals -Explain the details about the procedure for the known hydrate (Part 1) and designing the procedure used for the unknown hydrate (Part 2) . Be concise and descriptive. 2 -Describe any safe ty precautions taken within the procedure you followed. -Describe any other procedures you also tried (if applicable) . -This section should be detailed enough that another group could duplicate you r work, but do not include descriptions or analysis of the observed or calculated results so as to not overlap with the results and discussion sections. Results (1.5 point s): For Part 1, copper sulfate pentahydrate was studied to confirm the validity of the technique. Upon heating the sample of the hydrate , the percent by mass of water in the hydrate was determined, as can be seen in Table 1 Write a descriptive title for this table. Table 1: _______________________________________________________________________ CuSO 4 •5H 2O Mass of Hydrated Salt (g) Mass of Anhydrous Salt (g) Mass of Water Lost (g) Experimental Mass % Water Average Experimental Mass % Water Theoretical Mass % Water % Error Trial 1 Trial 2 If ___________% of the mass of the hydrate is water, _________% of the initial mass is due to the copper sulfate. For Table 2, the masses of hydrated salt and water were divided by their molecular weights to determine the moles of anhydrous salt and moles of water present. The ratio of moles of wa ter to anhydrous salt gave a molar ratio used to propose an empirical formula for the hydrated salt. 3 Write a de scriptive title for this table. Table 2: ________________________________________________________________________ Trial 1 Trial 2 CuSO 4 H2O CuSO 4 H2O Initial moles Mole Ratio (exact calculation) Empirical Formula (rounded mole ratio) Cu SO 4 •____ H2O Cu SO 4 •____ H2O For Part 2, an unknown hydrate was analyzed. Table 3 shows the mass percent water of hydration for the salt. Write a descriptive title for this table. Table 3: _______________________________________________________________________ ____SO 4 •XH 2O Mass of Hydrated Salt (g) Mass of Anhydrous Salt (g) Mass of Water Lost (g) Experimental Mass % Water Av erage Experimental Mass % Water Trial 1 Trial 2 For Table 4 the masses of hydrated salt and water were divided by their molecular weights to determine the moles of anhydrous salt and moles of water present. The ratio of moles of water to anhydrous salt ga ve a molar ratio used to propose an empirical formula for the hydrated salt. 4 Write a descriptive title for this table. Table 4: ________________________________________________________________________ Trial 1 Trial 2 _________ H2O _________ H2O Initial moles Mole Ratio (exact calculation) Empirical Formula (rounded mole ratio) ____SO 4 •____ H2O ____SO 4 •____ H2O Calculations (1 point) : The following sample calculation was used to determine the mass percentage water in CuSO 4 •5H 2O using experimental data from Table 1. Sample Calculation 1: Because the formula of CuSO 4 •5H 2O is known, the theoretical mass percentage of water in the hydrate from Table 1 was calculated (Sample Calculation 2) . The % error between the experimental and theoretical mass percentages were also calculated (Sample Calculation 3)using data from Table 1 : Sample Calculation 2: Sample Calculation 3 : 5 The following sample calculation was used to determine the moles of water and anhydrous salt from the masses using the molecular weights. Data from Table _______ was used. Sample Calculation 4 : Discussion (1 .5 point s): Using data from Part 1 of the experiment, the known hydrate , copper sulfate pentahydrate , was analyzed. As seen in Table 1, its percent by mass was determined experimentally as proof of concept with a __________% error. Briefly describe what this means about the potential validity of your results for analysis of an unknown hydrate. _________________________________________________________________________________ ____________________________________________________________ _____________________ _________________________________________________________________________________ _________________________________________________________________________________ _________________________________________________________________________ _______ As seen in Table 2, the masses of anhydrous salt can be calculated once the mass of water lost is determined. When converted to a molar ratio, the results should be consistent with the true formula of CuSO 4 •5H 2O with a ratio of 5:1, water to anhy drous salt. 6 Briefly describe how your results compared to the 5:1 ratio . State if your ratio was low or high, and explain why. _________________________________________________________________________________ ___________________________________________ ______________________________________ _________________________________________________________________________________ _________________________________________________________________________________ ________________________________________________________ ________________________ The same procedur e was followed for the determination of % mass of hydration and empirical formula mole ratio for the unknown hydrate, (circle ) MgSO 4•XH 2O /FeSO 4•XH 2O. The data in Tables 3, and 4 show the results of this analysis. It was determined that (circle ) MgSO 4•XH 2O/FeSO 4•XH 2O has a %mass of hydration of ____________________, and an empirical formula of __________________________________. There are several possib le sources of error and corrections that may have prevented each error. Fill in the table below, noting any experimental details or incongruences that may have led to errors in the results obtained. (“Human error ” is not an acceptable response , be more specific .) Error Possible Corrections 7 Conclusion (1 point ): Summarize the results obtained by this experiment: _________________________________________________________________________________ _________________________________________________________________________________ _________________________________________________________________________________ The procedur e developed during application of this experiment allowed / did not allow for a successful analysis of hydrate samples for the following reasons: _________________________________________________________________________________ ______________________________ ___________________________________________________ _________________________________________________________________________________ ___________________________ ______________________________________________________ Alternate methods or approaches : _________ ________________________________________________________________________ _________________________________________________________________________________ _________________________________________________________________________________ ______________________ ___________________________________________________________ Works Cited: ACS Style. Use at least one reputable source other than your lab manual on the space provided below. Bauer, R., Birk, J., Sawyer, D. Laboratory Inquiry in Chemistr y, 3rd ed.; Brooks/Cole Cengage Learning: Belmont, 2009. _________________________________________________________________________________ _________________________________________________________________________________ ____________________________________ _____________________________________________ _________________________________________________________________________________ 8