Lab Manual Jan 2018 PDF

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Laboratory Manual Chemistry 2 (MF 112)

Table of Contents Page Laboratory Report Format

2

Laboratory Safety Rules

5

Lab 1: An Application of Hess’s Law

6

Lab 2: Enthalpy of solutions

8

Lab 3: Aci d Content in Orange Juice

10

Lab 4: To Standardize a Solution of Sodium Hydroxide with Oxalic Acid

12

Lab 5: Gravimetric determination of nickel

14

Lab 6: Beer's law and its deviations

17

Lab 7: Ferrous ion chelating ability of green tea

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Lab 8 : Transition element complexes

21

Lab 9: Hydrolysis of methyl salicylate and crystallisation of salicylic acid

22

Lab 10: Solvent resistance of polymers

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Practical classes This course comprises 10 laboratory topics conducted over five practical sessions. Attendance of all practical classes is compulsory as they are a prerequisite for submission of practical reports. Session 1 2 3 4 5

Topic Lab 1: An Application of Hess’s Law Lab 2: Enthalpy of solutions Lab 3: Acid Content in Orange Juice Lab 4: To Standardize a Solution of Sodium Hydroxide with Oxalic Acid Lab 5: Gravimetric determination of nickel Lab 6: Beer's law and its deviations Lab 7: Ferrous ion chelating ability of green tea Lab 8 : Transition element complexes Lab 9: Hydrolysis of methyl salicylate and crystallisation of salicylic acid Lab 10: Solvent resistance of polymers

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Laboratory Report Format 

Students are required to conduct experiments in groups of four. One report is submitted per group for every experiment.

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All practical reports are due one week after each practical class. Marks will be deducted for each day of late submission.

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Each laboratory report is to be submitted together with a copy of the “Laboratory Report Submission Form”. Only if you require an acknowledgement receipt of your laboratory report, please prepare a duplicate copy of the form.

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Remember, you are not being graded solely on your results; therefore, a good, accurate representation of them, with any intelligent explanation or hypothesis for any data obtained, is critical.

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Avoid plagiarism. Plagiarism is illegal and it also demonstrates intellectual laziness i.e. lack of opinion and thinking. Ensure that you give proper credit when using facts from literature written by other authors by practicing proper citation and referencing. Group members who are co-authors of your reports and assignments must also be duly credited in the Report Submission Form.

Laboratory Report Expectations Laboratory reports should be presented in a professional manner with answers to all questions answered. The font to be used in each report is Times New Roman, 12 pt; 1.5 spacing. Paragraphs should be justified. A typical laboratory report comprises the following sections: 1. Laboratory Report Submission Form The title page is available for download on the LMS, it should contain the title of the experiment, name of group members (very important) and, the instructor’s name and course code (to ensure that your report does not get misplaced during submission). 2. Results Data reporting: This section contains all data collected from experiments. Data should be presented in properly labelled tables and figures (graphs, charts and images). Tables should not contain vertical lines and captions should be placed on top of the table (Remember the phrase “Table-top”). Captions for figures should be placed below the figure. If the figure is a graph, it should be plotted using Microsoft Excel. Tutorials on plotting graphs and doing calculations with Microsoft Excel are freely available online. Examples on next page. Calculations: Include a sample calculation in the report as this would be graded. However, it is strongly recommended that students learn how to do calculations using Microsoft Excel to avoid mistakes. 3. Conclusion Briefly summarize the findings supported by the data. The conclusion should match the objectives of the experiment.

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TABLE 4

Total phenolic content (TPC) and ascorbic acid equivalent antioxidant capacity (AEAC) of fresh and microwave-dried leaves of Thunbergia laurifolia (fresh weight)

Leaf sample

TPC (mg GAE /100 g)

AEAC (mg AA/100 g)

Fresh

656

526

Microwave-dried

902

968

Abbreviations: GAE = gallic acid equivalent and AA = ascorbic acid.

FIGURE 2

Leaves and flowers of Thunbergia laurifolia

4. Questions Answer all questions in laboratory manual. These would be graded. Facts obtained from literature must be duly acknowledged with proper citations. All citations in answers must be listed in the reference section. The example below was taken from a student’s thesis that cites multiple research papers. For a laboratory report, it is more common to cite textbooks. FIGURE 2 shows the leaves and flowers of Thunbergia laurifolia. Results from this study supported earlier findings of Chan and Lim (2006) that the TPC and AEAC of microwave-dried T. laurifolia leaves were significantly higher than fresh leaves (TABLE 4). The higher antioxidant properties of microwave-dried T. laurifolia leaves can be explained by the short drying time and microwave inactivation of degradative enzymes naturally present in the leaves (Gulati et al. 2003). Note: the difference in style by citing the author directly and indirectly. If there are more than three authors, the surname of the first author is accompanied by “et al.”, short for et alia for referring to co-authors. If the names of authors are unknown, “Anon.”, short for anonymous e.g. (Anon. 2011).

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5. References Faculty of Applied Sciences, UCSI University uses a modified Harvard referencing system for all reports, assignments and theses. References are sorted alphabetically according to the surnames of the first author. Different literature is cited differently as shown below: Books Silberberg, M. S., and Duran, R. 2002. Chemistry: the molecular nature of matter and change. 6th Ed. New York: McGraw-Hill. Research papers (Journals) Mitsui, K., Kaneshiro, T., Tanaka, S., and Morishi, M., 2004. Increase in leukocyte counts of mice administered with Ganoderma lucidum. Journal of Nippon Food Science, 4, 231-240. Websites (with author, organization and date) Grossman, M., 2001. Technology and Diplomacy in the 21st Century [Online]. U.S. Department of State. Available from: http://www.state.gov/p/6580.html [Accessed 21 May 2004]. Websites (undated with no author) Royal Institute of British Architects, n.d., Shaping the Future: Careers in Architecture [Online]. Available from: [Accessed 21 May 2004].

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Laboratory Safety Rules The dangers associated with contact with hazardous chemicals, flames, are very well documented, and as a result, laboratories are constructed and procedures are carried out with these dangers in mind. Hazardous chemical fumes are, for example, vented into the outdoor atmosphere with the use of fume hoods. Safety showers for diluting spills of concentrated acids on clothing are now commonplace. Eyewash stations are strategically located for the immediate washing of one’s eyes in the event of accidental contact of a hazardous chemical with the eyes. Fire blankets, extinguishers, and sprinkler systems are also located in chemistry laboratories for immediately extinguishing flames and fires. A variety of safety gear, such as safety glasses and shields are also available. All laboratory personnel should carefully study the list below: 1. Safety glasses must be worn at all times by students and instructors. Visitors to the lab must be appropriately warned and safety glasses made available to them. 2. Fume hoods must be used when working with chemicals that may produce hazardous fumes. 3. The location of fire extinguishers, safety showers, and eyewash stations must be known. 4. All laboratory workers must know how and when to use the items listed in number 3. 5. There must be no unsupervised or unauthorized work going on in the laboratory. 6. A laboratory is never a place for practical jokes or pranks. 7. The toxicity of all the chemicals you will be working with must be known. Consult the instructor, material safety data sheets (MSDSs), safety charts, and container labels for safety information about specific chemicals. 8. Eating, drinking, or smoking in the laboratory is never allowed. Never use laboratory containers (beakers or flasks) to drink beverages. 9. Shoes (not open-toed) must always be worn; hazardous chemicals may be spilled on the floor or feet. 10. Long hair should always be tied back. 11. Mouth pipetting is never allowed. 12. Cuts and burns must be immediately treated. Use ice on new burns and consult a doctor for serious cuts. 13. In the event of acid spilling on one’s person, flush thoroughly with water immediately. Be aware that acid–water mixtures will produce heat. Removing clothing from the affected area while water flushing may be important, so as to not trap hot acid–water mixtures against the skin. Acids or acid–water mixtures can cause very serious burns if left in contact with skin, even if only for a very short period of time. 14. Weak acids (such as citric acid) should be used to neutralize base spills, and weak bases (such as sodium carbonate) should be used to neutralize acid spills. Solutions of these should be readily available in the lab in case of emergency. 15. Dispose of all waste chemicals from the experiments according to your instructor’s directions. 16. In the event of an accident, report immediately to your instructor, regardless of how minor you perceive it to be. 17. Always be watchful and considerate of others working in the laboratory. It is important not to jeopardize their safety or yours. 18. Always use equipment that is in good condition. Any piece of glassware that is cracked or chipped should be discarded and replaced. 5

Lab 1: An Application of Hess’s Law

Objectives To determine the enthalpy change for the hydration of anhydrous copper sulphate that cannot be measured directly CuSO4 + 5H2O → CuSO4 .5H2O

Materials and methods Reagents/

How required

Anhydrous copper sulphate CuSO4 (s) Hydrated copper sulphate, CuSO4.5H2O (s)

Apparatus

5g

10g

Size

Expanded styrofoam cups Thermometer

Number 2

-10 to 110°

Electric balance Measuring cylinder

Quantity

1 shared

50 mL

1

Enthalpy of solution for anhydrous copper sulphate 1. Weigh approximately 5 g of anhydrous CuSO4. Accurately record the mass to at least three decimal places. 2. Pour 50 mL of water, using a measuring cylinder, into a Styrofoam cup. Record the initial temperature of water. 3. Add the anhydrous CuSO4 and stir with the thermometer. Determine the maximum change in temperature. Enthalpy of solution for copper sulphate pentahydrate 4. Weigh approximately 10 g of hydrated CuSO4.5H2O. Accurately record the mass to at least three decimal places. 5. Pour 50 mL of water, using a measuring cylinder, into a Styrofoam cup. Record the initial temperature of water. 6. Add the hydrated CuSO4.5H2O and stir with the thermometer. Determine maximum change in temperature

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Calculations The enthalpy change when dissolving copper sulphate (ΔHsolution) can be calculated using the equation below: q = mass of water x ΔT x c The specific heat capacity of water is 4.184 J/g*K 

Calculate the ΔHsolution for one mole of anhydrous CuSO4 (159.62 g/mol) CuSO4 (s) → Cu2+ (aq)+ SO42- (aq)

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Calculate the ΔHsolution for one mole of hydrated CuSO4.5H2O (249.69 g/mol) CuSO4.5H2O (s) → Cu2+ (aq)+ SO42- (aq) + 5H2O (l)

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Combine the two thermochemical equations above to find the enthalpy change for the hydration (ΔHhydration) of anhydrous copper sulphate CuSO4 (s) + 5H2O (l) → CuSO4 .5H2O (s)

Questions 1. Explain the differences between the ΔHsolution of anhydrous CuSO4 and hydrated CuSO4.5H2O. 2. It is not possible to calculate the enthalpy of formation (∆Hformation) of carbon monoxide, CO, directly. Suggest a reason for this. In an experiment to determine the ∆Hformation of CO from the information below: CO (g) + ½O2 (g) → CO2 (g) C (g) + O2 (g) → CO2 (g)

∆H = -286 kJ mol-1 ∆H = -395 kJ mol-1

Calculate ∆Hformation CO (g): C(g) + ½O2 (g) → CO (g)

∆H = ? kJ mol-1

3. Calculate the ∆Hformation of methane, CH4 from the enthalpies of combustion of carbon, hydrogen and methane: C (g) + O2 (g) → CO2 (g) H2(g) + ½O2(g) → H2O (g) CH4 (g) + 2O2 (g) → CO2 (g) + 2H2O (g)

∆H = -395 kJ mol-1 ∆H = -286 kJ mol-1 ΔH = -890 kJ mol-1

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Lab 2: Enthalpy of solutions

Objective To find the enthalpy of solution (ΔHsolution) of potassium nitrate and sodium hydroxide in water

Materials and methods Reagents Potassium nitrate, KNO3 (s) Sodium hydroxide, NaOH (s) Apparatus Electric balance Thermometer Expanded polystyrene cups Cardboard lid Measuring cylinder

Quantity about 10 g 4g Size -10 to 100°C

100 mL

Number shared 1 2 1 1

1. Weigh 0.1 mole of potassium nitrate (101.10 g/mol). Accurately record the weight to at least three decimal places. 2. Pour 100 mL of water, using a measuring cylinder, into a Styrofoam cup. Record the initial temperature of water. 3. Add the potassium nitrate and stir with the thermometer. Determine the lowest temperature reached. 4. Thoroughly wash the Styrofoam cup with distilled water and repeat the experiment using 0.1 mole of solid sodium hydroxide (40.00 g/mol). 5. By the end of the experiment, ensure that you have recorded the following information:  Weight of potassium nitrate  Weight of sodium hydroxide  Initial temperature when measuring ΔHsolution of potassium nitrate  Initial temperature when measuring ΔHsolution of sodium hydroxide  Temperature after dissolving potassium nitrate  Temperature after dissolving sodium hydroxide

Assumptions   

There are no heat losses from the calorimeter That the thermometer absorbs no heat A 1°C change in temperature of 1 mL solution requires 4.184 J

Calculations 

Calculate the change in temperature after the addition of potassium nitrate and sodium hydroxide

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Calculate the ΔHsolution of potassium nitrate and sodium hydroxide using the equation below: q = mass of water x ΔT x c The specific heat capacity of water is 4.184 J/g*K Calculate the heat of reaction (ΔHrxn) for dissolving one mole of potassium nitrate and sodium hydroxide

Questions 1. Give an example of a commercial application of an exothermic reaction and a commercial application of an endothermic 2. Explain why exothermic reactions are assigned a negative ΔH. 3. The assumptions made for the calorimetric calculation are approximations. Explain how this is so. Does this mean that the calculations are invalid?

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Lab 3: Acid Content in Orange Juice

Objective To determine the acid content in orange juice in terms of citric acid equivalent

Materials and methods About 100 mL of orange juice is required. If the juice is turbid, centrifugation or filtration may be required to remove solid particles. Reagents sodium hydroxide solution, NaOH Phenolphthalein

How required 0.1 M

Quantity 100 mL

solution

A few drops

Apparatus Burette Burette stand and clamp Electric balance Conical flask Conical flask

Size 50 mL

Number 1 1 Share 1 1

20 mL 250 mL

1. Dispense about 100 mL of titre (NaOH) into a clean, dry beaker and bring it back to your workbench. 2. Using a funnel, load the titre into the burette and record the initial reading which need not be 0.0 mL. 3. Place a white tile under the burette and then measure 20 mL using a measuring cylinder of the juice and pour into a 250 mL conical flask. Add about 50 mL of distilled water and 4 drops of phenolthalein. 4. Do a rapid titration to get the approximate titre volume. Stop at the first permanent indicator colour change. 5. Repeat the titration to obtain a more accurate reading. Dispense acid as before but proceed drop by drop when within 2 mL of previous titre. Remember to record all data in the table below: TABLE

Titre volume of NaOH standard solution Titration replicates

Approximate 1

Accurate 2

3

Initial reading (mL) Final reading (mL) Titre volume (mL) Average titre volume of 2nd and 3rd attempt 10

6. Repeat 2 consistent titres (within 0.1-0.2 mL of each other).

Calculations Citric acid is a simple organic acid with one hydroxyl group and three carboxyl groups

 Calculate the number of moles of citric acid equivalent according to the equation below: 3NaOH + citric acid → sodium citrate + 3H2O  Calculate the mass of citric acid equivalent present in 20 ml of orange juice  Calculate the percent, weight per volume (% w/v) of citric acid equivalent in orange juice

Questions 1. What is the molar mass of citric acid? 2. Orange juice contains vitamin C, ascorbic acid. Would vitamin C affect the reading of this experiment? Can the quantitative method in this experiment be used to distinguish citric acid from other acids? 3. What does the word “equivalent” in citric acid equivalent mean? Hint: citric acid is not the only acid present in orange juice. Similar terms include gallic acid equivalent, quercetin equivalent and ascorbic acid equivalent. 4. If the orange juice is left standing for an extended period of time, will the acid content change? Explain. Hint: Consider the CO2 content of the atmosphere.

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Lab 4: Standardizing a Solution of Sodium Hydroxide with Oxalic Acid

Objectives To prepare a standard solution of oxalic acid To standardize a solution of sodium hydroxide with the prepared oxalic acid solution

Materials and methods 1. A total of 1.6 g of accurately weighed oxalic acid dihydrate crystals would be provided. Dissolve it in some distilled water and dilute the solution to 250 mL in a volumetric flask. Mix the solution by inversion. 2. Dispense about 100 mL of titre (non-standard NaOH) into a clean, dry beaker and bring it back to your workbench. 3. Using a funnel, load the titre into the burette and record the initial reading which need not be 0.0 mL. 4. Place a white tile under the burette and then pipette 25 mL of oxalic acid standard solution into a 250 mL conical flask. Add 4 drops of phenolthalein. 5. Do a rapid titration to get the approximate titre volume. Stop at the first permanent indicator colour change. 6. Repeat the titration to obtain a more accurate reading. Dispense acid as before but proceed drop by drop when within 2 mL of previous titre. Remember to record all data in the table below: TABLE

Titre volume of a non-standard NaOH solution Titration replicates

Approximate 1

Accurate 2

3

Initial reading (mL) Final reading (mL) Titre volume (mL) Average titre volume of 2nd and 3rd attempt 7. Repeat 2 consistent titres (within 0.1-0.2 mL of each other).

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Calculations Oxalic acid is a small organic acid comprising two carboxyl groups linked to one another. Note: The oxalic acid provided in this experiment is in the dihydrate form.

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Calculate the molar mass of oxalic acid dihydrate Calculate the concentration of the oxalic acid standard solution...