CHM1052 Exercise 4 Iron Oxalate Proforma 2017 PDF

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Iron Oxalate

CHM1052: Exercise 4 Proforma – Synthesis and Determination of the Composition of an Iron Oxalate Complex Name: LEANNE TAN YANN LING Partner: TAN TIONG WEI, TAY KIM YANG, TAN MEI VEEN Student I.D. number: 29344468 Demonstrator: Krystle, Yaw Group Letter: 3-B Day & Session: 9.00 a.m. – 1.00 p.m. Student Code of Conduct: I certify that I understand and have abided by the university plagiarism policy: (http://policy.monash.edu.au/policy-bank/academic/education/conduct/plagiarism-policy.html). To the best of my knowledge this practical report contains no previously published material or other students’ work. I have not participated in unauthorised collaboration when preparing this work. Signature: _____________________________

Date: 19/4/2018

Aim: To synthesis iron oxalate complex and determine the overall stoichiometry of the molecular formula of iron oxalate complex, Kz[Fex(C2O4) y].wH2O

/3 Method: Part A: Hot, dissolved K2C2O4.H2O was added to room temperature FeCl3 solution.

The mixture is placed in the ice bath until green crystals are formed The crystals are the rinsed with cold distilled water, dried using vacuum suction and weighed.

Part B: 3 samples of approxmately 0.1g of iron oxalate complex is weighed and dissolve with 10 mL of distilled water and 25mL of 2M H2SO4 into 3 seperate conical flask.

5 labelled 25mLvolumetric flask is inserted with 0.0, 2.5, 5.0, 7.5, and 10mL of standrd solution. 5mL of 2M H2SO4 and 10% of KSCN solution to each side and add distilled water to make up the mark of the comical flask. The absorbance of these solution is measured.

A vial and cap are weighed. Approximately 0.01g of iron oxalate complex is added into the vial and transfered into a 25mL volumetric flask and the flask is made to the mark by adding distilled water. This solution is a stock solution.

Part C: Known concentration of Fe(III) standard solution is collected. The burette is the rinsed and filled with the standard solution

A labelled 25mL of volumetric flask is added with 1.0mL of the stock solution. 5mL of 2M H2SO4 and 10% of KSCN solution is added into the flask and the flask is made to its mark by adding distilled water. The absorbance of the mixture is measured.

The mixture is heated for 30-50 seconds. Then, titration is carried out immediatelywith permanganate solution until a permanent pink tinge appear which indicates the end point of the titration.

Part D: Coefficient x,y,w,z is from Kz[Fex(C2O4) y].wH2O is calculated using the data collected from part B and C

/4

2

Iron Oxalate

3

Iron Oxalate

Results: Space for Notes/Observations made throughout exercise. When the hot K2C2O4.H2O solution is added to the cold ferric chloride solution, the mixture tuns green in colour. After crystallisation, green solids are formed. When FeCl2. 6H2O dissolved in distilled water to form a brick-red colour solution.

/1 Part A: Synthesis of Iron Oxalate Complex: Mass of iron (III) chloride anhydrous: 0.7831g Final mass of oxalate complex: 0.0136g /1 Part B: Oxalate Analysis – Titrations: Concentration of KMnO4 solution : 0.02M 4

Sample

1

2

3

Mass of complex (g) in sample

0.102

0.103

0.103

Final Reading (mL)

29.4

42.6

50.0

Initial Reading (mL)

17.0

29.9

37.7

Titre (mL)

12.4

12.7

12.7

n(KMnO4) (mol) in titre

2.52 x 10^-4

2.54 x 10-4

2.54 x 10-4

n(Oxalate) (mol) in sample

6.30 x 10-4

6.35 x 10-4

6.35 x 10-4

m(Oxalate) (g) in sample

0.0555

0.0559

0.0559

%m(Oxalate)  m(oxalate) x 100 m(complex)

0.0555 ×100 0.102 ¿ 54.41 %

0.055 9 ×100 0. 10 3 =54.27%

4

0.0559 ×100 0.103 =54.27%

Iron Oxalate

Average1 concordant values2 %m(Oxalate) : 54.32% /6 Part C: Iron Analysis by Ultra-Violet/Visible Spectrophotometry (UV/VIS): Concentration of Fe(III) standard solution provided: 10ppm mol/L ∴ Concentration of the Fe(III) standard solution in mg/L: 10 mg/L /0.5 Mass of complex in your stock sample solution: 0.0136g Iron Oxalate Sample

Solutions Standards

1

2

3

4

5

Volume Delivered (mL)

0.00

2.50

5.00

7.50

10.00

Concentration (mg/L)  C1V1 = C2V2

0.00

1.00

2.00

3.00

4.00

Absorbance

0.000

0.117

0.248

0.380

0.511

Final Reading (mL) Initial Reading (mL)

0.328 /2.5

Plot a graph (calibration curve) of concentration vs. absorbance for your Iron (III) standards on a computer using either a) the software on the UV-Vis computers or b) Excel. Determine the equation for the line of best fit, and thus the concentration of your diluted Fe(III) sample. Print out your calibration curve and attach it to your lab report; ensure the graph is labelled, including a title, labels on the axes of the graph. Don’t forget to report line of best fit and the R2. /2 Concentration (mg/L) of iron in your diluted sample: 2.65 mg/L

/0.5 Concentration (mg/L) of iron in your stock sample: NB: C1V1 = C2V2 C1(1.0) = (2.65) (25) C1 = 66.25 mg/L /0.5 Mass iron (g) in the complex you weighed and made up into your stock sample solution: m(mg) = C(mg/L) x V(L) 1Be sure to indicate the samples you use to determine your average.

2Concordant values = concordant %m(oxalate) values (within 1%), NOT titre volumes ! 5

Iron Oxalate

mass of iron =

66.25 ×

25 1000

= 1.66 mg

/1 %mass iron in the complex you weighed and made up into your stock sample solution: %m(Fe3+) = [m(Fe3+) g/m(complex)g] x 100

1.66 mg × 100 0.0136

%m(Fe3+) =

¿

0.00166 g ×100 0.0136 =12.21% /1

Part D: Calculations Determine the mole ratio of iron (III) to oxalate (Fe3+:C2O42-) in the sample. Assume you have 100 g complex, and round your answer to the nearest whole number.

From above: Average %m(Oxalate) (C2O42-) in the complex (from Part B)

54.32%

Average %m(Iron) (Fe3+) in the complex (from Part C)

12.21%

Use these results to determine the mole ratio of Fe3+:C2O42- in the complex: Assume you have 100 g complex Mw(Fe3+)

= 55.85 g/mol

%m(Fe3+) = 12.21%

Mw(C2O42-)

= 88.02 g / mol

%m(C2O42-)

= 54.32 %

=12.21g in 100 g n(Fe3+)

= 54.32 g in 100 g

= m(Fe3+)/Mw(Fe3+)

n(C2O42-)

= 0.219 mol

= m(C2O42-)/Mw(C2O42-) = 0.617 mol

To determine the molar ratio divide by smallest no. of moles and round your answer to the nearest whole number (if a ratio value comes up as a half-integer (e.g. 1.5, 2.5, etc.) multiply both of your answers by 2). Ratio (Fe3+)

= n(Fe3+)/ nsmallest

Ratio (C2O42-) 6

= n(C2O42-)/ nsmallest

Iron Oxalate

=1

=3

=x

=y

Therefore molar ratio of Fe3+:C2O42- = 1: 3 = x : y (in formula) /5 Determine the stoichiometric ratio of potassium (K+) in the complex: Fex(C2O4)y is an anionic species (negatively charged). Since the overall complex K z[Fex(C2O4)y] is neutral, the stoichiometric ratio of K+: Fex(C2O4)y will be such that the negative charge from the Fex(C2O4)y is balanced by the positive charge from the K+. Charge (Fe3+) = +3

Charge (C2O42-) = -2

no. Fe3+ ions/complex = x

=1

no. C2O42- ions/complex = y

=3

Charge contributed by Fe3+

= +3

Charge contributed by C2O42-

= -6

Overall charge Fex(C2O4)y

= -3

Charge (K+) = +1

no. K+ ions required to balance charge = 3 = z



/2 Collate your information, and determine the waters of hydration (w) for the complex: Assume 100 g complex K+

Fe3+

C2O42-

H2O

Mw (g/mol)

39.10

55.85

88.02

18.00

% by mass

24.13%

12.21%

54.32%

9.34%

No. moles (n)

0.6171

0.2186

0.6171

0.5189

Molar ratio

z=3

x =1

y =3

w=2 /2

Determine the mass of K+ in 100g of complex: n(K+)

= (z/y) x n(C2O42-) = 0.6171 g/mol

m(K+)

= n(K+) x Mw(K+) = 24.13 g = % by mass K+

Determine the % by mass and the ratio of H2O in the complex: % by mass (H2O)

= 100% - %m(K+) - %m(Fe3+) - %m(C2O42-) = 9.34 % = m (H2O) (g) in 100 g complex

n(H2O) = m(H2O)/Mw(H2O) = 0.5189 mol Ratio

= n(H2O)/n(Fe3+) x (x) 7

Iron Oxalate

= 2 (Round to the nearest whole number) =w

/4

Therefore, the formula of the complex is: NB: Substitute values into the formula Kz[Fex(C2O4)y].wH2O

K3[Fe(C2O4)3].2H2O

/1 Discussion: Discuss your results and relate them back to the aim. Don’t forget to report actually numerical results and to discuss errors that were made including what impact they had on the final result. Include a suggestion as to another technique that you could use to confirm your analysis. The synthesized Iron(III) Oxalate complex from part A resulted the average mass percentages of 54.32%. The percentage by mass of K+, Fe3+, C2O42-, H2O are 24.13%, 12.21%, 54.32%, 9.34% with the number of moles of 0.6171 mol, 0.2186 mol, 0.6171 mol, 0.5189 mol respectively. Furthermore, the value of x, y, w, and z are 1, 3, 2 and 3 respectively which forms final the empirical formula of K3[Fe(C2O4)3].2H2O. Although the empirical formula calculated is correct, but the mass percentage is relatively low. This may be due to some loss of the Iron (III) chloride when transferring the compound to the conical flask. Other than that, loss of solids may occur due to the used of the glass rod for stirring to dissolve the solid in the potassium oxalate monohydrate solution. Also, the accuracy of the absorbance in part B may be affected by the incorrect handling of the cuvette during the spectrophotometry test such as presence of fingerprints and water droplets. In the dilution steps of part B and C, excess addition of distilled water that exceeds the mark of the volumetric flask affected the concentration of the standard solution and the diluted solution causing inaccurate volume of titre and inaccurate absorbance in part B and C respectively. Moreover, the intensity of pink colour of every trial in the titration of part B may vary and this is caused by inconsistency of addition of the titre solution. To confirm the identity of the compound synthesised, Thin Layer Chromatography (TLC) can be carried out to compare the Rf value of the product and the reference compound.

8

Iron Oxalate

/6 Conclusion: The compound synthesized is Iron(III) Oxalate complex and the average mass percentages of 54.32%. The percentage by mass of K+, Fe3+, C2O42-, H2O are 24.13%, 12.21%, 54.32%, 9.34% with the number of moles of 0.6171 mol, 0.2186 mol, 0.6171 mol, 0.5189 mol respectively. The value of x, y, w, and z are 1, 3, 2 and 3 and the final empirical formula of the compound is K3[Fe(C2O4)3].2H2O.

/2 Total Score ________/45 Demonstrator Feedback: ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ Marking Scheme: Housekeeping:  Cleaning the glassware you use and placing it back wherever you obtained it from  Cleaning up all workspaces including your bench, the side benches and the fume cupboard General Aim 3 marks Method 4 marks Results Notes & Observations 1 mark PART A 1 mark PART B 6 marks PART C 8 marks Calculation 14 marks s Discussion 6 marks Conclusion 2 marks Total 45 marks - 1 mark/5 mins Penalties Arriving to lab after 2:05 PM - 2 marks Poor attitude - 2 marks Poor housekeeping/not cleaning up to - 5 marks Poor writing/presentation - 2 marks Student code of conduct not signed - 5 marks Laboratory book/pro forma not signed off by TA and/or copy not submitted 9

Iron Oxalate Late submission of report

- 4.5 marks/day

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