Determination of the Formula of Hydrated Iron (II) Sulphate Crystals Essay

  1. Hypothesis

I predict that the expression of hydrated Iron ( II ) sulfate crystals can be by experimentation determined and stoichiometrically expressed. The chemical equation involved in this experiment is written as:

FeSO4 a?™ x H2O ; where ten is the unknown coefficient.

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In this experiment, 10 gms of the hydrated Iron ( II ) sulfate will be heated to go forth behind the anhydrous sample which will be weighed and the mass and molar ratios determined, together with that of H2O. The unknown coefficient will so be obtained and the expression determined.

  1. Background

Wilbraham and others ( 1997 ) , claim that “water molecules are an built-in portion of the crystal construction of many substances. The H2O in a crystal is called the H2O of hydration or H2O of crystallization” . The expression of the hydrate consists of the chemical expression of the anhydrous sample, followed by a point and the figure of H2O molecules that crystallize with one expression unit of the sample. This expression can be obtained by experimentation by heating the sample to drive off the H2O of crystallisation.

III.Procedure of the Experiment

  1. Materials needed:

Analytic balance

Bunsen burner

Crucible

Crucible tongs

Clay trigon

10.0 gms of hydrated Iron ( II ) sulfate

B. Procedure:

1. Clean the crucible thoroughly and topographic point it on a clay trigon.

2. Heat the crucible utilizing a Bunsen burner for 2 -3 proceedingss to drive off captive H2O on the walls of the melting pots.

3. Let the crucible base and cool.

4. Weigh the cooled melting pot.

5. Record the weight of the melting pot.

6. Measure about 10 gms of hydrated Iron ( II ) sulfate on the analytical balance.

7. Put the weighed hydrated Iron ( II ) sulphate sample in the melting pot.

8. Weigh the crucible with the sample and record the weight.

9. Put the melting pot with the sample on the clay trigon on a ring base and heat it for 10- 15 proceedingss, gently at foremost, so strongly, until there is a noticeable alteration in the colour of the sample. In this instance, the sample turns green to white.

10. Let it stand to chill.

11. Weigh the sample and record the weight measuring.

12. Repeat stairss 9-11 until at least 2 similar weight measurings are obtained.

13. Repeat stairss 1-15 to execute tallies 2, 3 and 4.

IV. Consequences

Datas Gathered:

Mass of the crucible = 27. 50 gms

Mass of the crucible + sample ( hydrous FeSO4 ) = 37.50 gms

Mass of hydrated FeSO4 ( FeSO4 + H2O ) = 10 gms

Table 1: Weight Measurements of Anhydrous FeSO4 Salt Obtained

Reading 1

Mass in gms

Reading 2

Mass in Grams

Reading 3

Mass in Grams

Reading 4

Mass in Grams

Run 1 5.80 5.65 5.50 5.50
Run 2 5.70 5.40 5.35 5.35
Run 3 5.80 5.60 5.45 5.45
Run 4 5.60 5.50 5.40 5.40

Table 2: Average Weight Measurements of Anhydrous FeSO4 Salt

Run 1 5.65 gms
Run 2 5.45 gms
Run 3 5.57 gms
Run 4 5.48 gms

V. Analysis

  1. Initial phases:

The mean weight measurings of anhydrous FeSO4 obtained for each tally were tabulated and are shown above.

I believe that some anomalous consequences were obtained in the weight measurings of the sample. However, these mistakes are negligible since an analytical balance was used and was accurately calibrated before each usage. The weight measuring mistakes are due to some sample residues already on the graduated table.

2. Calculation

For Run 1:

  1. The mass of anhydrous salt ( FeSO4 ) :5.5 g
  2. Mass of H2O of crystallisation driven off = 10.0 gms – 5.5 gms =4.5 gms.
  3. The per centum of H2O of crystallisation = 4.5grams X 100 / 10 gms =45 %.
  4. The mass ratio of FeSO4 to H2O =5.50 gms: 4. 50 gms
  5. To change over the mass ratio to mole ratio, the molecular mass of each species is divided by the expression weight of each species.

Formula weight of FeSO4: Fe = 1 ten 55.85 = 55.85

S = 1 ten 32.07 = 32.07

O = 4 x16.00 =64.00

151.92 g/mole

Formula weight of H2O: H = 2 ten 1.00 = 2.00

O = 1 ten 16.00 =16.00

18 g / mole

Number of moles of FeSO4 = Weight in gms / Formula weight

= 5.50 g / 151.92 g/mole

=0.03620 mole

Number of moles of H2O = Weight in gms / Formula weight

= 4.50 g / 18 g/mole

=0.25 mole

mole ratio of FeSO4: H2O = 0.25 mole / 0.03620 mole =6.90? 7.00

Formula of Hydrated Iron ( II ) Sulphate = FeSO4 a?™ x H2O

=FeSO4 a?™ 7H2O

For Run 2:

  1. The mass of anhydrous salt ( FeSO4 ) :5.35 gms
  2. Mass of H2O of crystallisation driven off = 10.0 gms –5.35grams =4.65 gms.
  3. The per centum of H2O of crystallisation = 4.65grams X 100 / 10 gms =46.5 %.
  4. The mass ratio of FeSO4 to H2O =5.35 gms: 4.65 gms
  5. To change over the mass ratio to mole ratio, the molecular mass of each species is divided by the expression weight of each species.

Formula weight of FeSO4: Fe = 1 ten 55.85 = 55.85

S = 1 ten 32.07 = 32.07

O = 4 ten 16.00 =64.00

151.92 g/mole

Formula weight of H2O: H = 2 ten 1.00 = 2.00

O = 1 ten 16.00 =16.00

18 g / mole

Number of moles of FeSO4 = Weight in gms / Formula weight

= 5.35 g / 151.92 g/mole

=0.03521 mole

Number of moles of H2O = Weight in gms / Formula weight

= 4.65 g / 18 g/mole

=0.25833 mole

mole ratio of FeSO4: H2O = 0.25833 mole / 0.03521 mole =7.33 ? 7.00

Formula of Hydrated Iron ( II ) Sulphate = FeSO4 a?™ x H2O

=FeSO4 a?™ 7H2O

For Run 3

  1. The mass of anhydrous salt ( FeSO4 ) :5.45 g
  2. Mass of H2O of crystallisation driven off = 10.0 gms – 5.45 gms =4.65 gms.
  3. The per centum of H2O of crystallisation = 4.65grams X 100 / 10 gms =46.5 %.
  4. The mass ratio of FeSO4 to H2O =5.45 gms: 4.65 gms
  5. To change over the mass ratio to mole ratio, the molecular mass of each species is divided by the expression weight of each species.

Formula weight of FeSO4: Fe = 1 ten 55.85 = 55.85

S = 1 ten 32.07 = 32.07

O = 4 ten 16.00 =64.00

151.92 g/mole

Formula weight of H2O: H = 2 ten 1.00 = 2.00

O = 1 ten 16.00 =16.00

18 g / mole

Number of moles of FeSO4 = Weight in gms / Formula weight

= 5.45 g / 152.92 g/mole

=0.03587 mole

Number of moles of H2O = Weight in gms / Formula weight

= 4.55 g / 18 g/mole

=0.25278 mole

mole ratio of FeSO4: H2O = 0.25278 mole / 0.03587 mole =7.05 ? 7.00

Formula of Hydrated Iron ( II ) Sulphate = FeSO4 a?™ x H2O

=FeSO4a?™ 7H2O

For Run 4

  1. The mass of anhydrous salt ( FeSO4 ) :5.40 g
  2. Mass of H2O of crystallisation driven off = 10.0 gms – 5.40 gms =4.60 gms.
  3. The per centum of H2O of crystallisation = 4.60grams X 100 / 10 gms =46 %.
  4. The mass ratio of FeSO4 to H2O =5.40 gms: 4.60 gms
  5. To change over the mass ratio to mole ratio, the molecular mass of each species is divided by the expression weight of each species.

Formula weight of FeSO4: Fe = 1 ten 55.85 = 55.85

S = 1 ten 32.07 = 32.07

O = 4 ten 16.00 =64.00

151.92 g/mole

Formula weight of H2O: H = 2 ten 1.00 = 2.00

O = 1 ten 16.00 =16.00

18 g / mole

Number of moles of FeSO4 = Weight in gms / Formula weight

= 5.40 g / 151.92 g/mole

=0.03554 mole

Number of moles of H2O = Weight in gms / Formula weight

= 4.60 g / 18 g/mole

=0.25556 mole

mole ratio of FeSO4: H2O = 0.25556 mole / 0.03531 mole =7.19 ? 7.00

Formula of Hydrated Iron ( II ) Sulphate = FeSO4 a?™ x H2O

=FeSO4 a?™ 7H2O

Three important figures were used in the finding of the mole ratios of FeSO4 and H2O since the measuring of uncertainness is+0.01 for weight measurings, which is equal to 3 important figures.

  1. Discussion

In all 4 tallies, the measurings of the last 2 readings becomes the mass of the anhydrous salt ( delight refer to postpone 1 and the graph ) . Hence, the expression of hydrated Iron ( II ) sulfate can be obtained by experimentation. In this peculiar experiment, all four tallies gave the same expression, which is:FeSO4 a?™ 7H2O.For every expression unit of FeSO4, there are 7 molecules of H2O.

The expression obtained in this experiment for hydrated Iron ( II ) sulfate is the same as what Wilbraham and others ( 1997 ) , listed as one of the common hydrates with a chemical name of Iron ( II ) sulfate heptahydrate ; a chemical expression of FeSO4 a?™ 7H2O and a common name of “green vitriol” .

The per centum mistakes of the concluding values obtained in all tallies of the experiment were calculated and are shown below:

Percentage Error = mistake / ?

Where ? = true value ; in this instance, is equal to 7.00;and mistake = ? x1 / N.

? x1 =Run 1 + Run 2 + Run 3+ Run 4

N

=6.90 + 7.33 + 7.05 + 7.19

4

= 0.12

Relative mistake = 0.12 / 7.00 ten 100 = 1.71 %

The true value of the mole ratios of FeSO4: H2O is equal to 7.00. The per centum mistake of all concluding values compared to the true value is 1.71 % . Therefore, it can be concluded that the experimental consequences were comparatively accurate.

VI. Evaluation

The method used in the experiment was suited as proven by the little per centum mistake and the high dependability of consequences. Some anomalous consequences could hold been obtained during the assorted weight measurings due to the presence of residues on the graduated table. However, these are negligible since a carefully graduated analytical balance was used in every reading for all tallies of the experiment.

I believe that there were no procedural mistakes in the experiment committed. The mistakes lie on the concluding values obtained as compared to the true or absolute value of the mole ratio of FeSO4 to H2O.

The per centum mistake in the concluding values of all tallies of the experiment is merely 1.71 % , which means that the experiment gave comparatively accurate consequences compared to the true value of 7.00.

The experimental methods and processs were dependable as proven by the comparatively “similar” concluding values obtained in all tallies of the experiment.

The consequence of mistakes of weight measurings on the concluding values is negligible since the per centum mistake of the concluding value is merely 1.71 % . As a regulation, the smaller the value of the per centum mistake, the more accurate are the consequences. Hence, I believe that the consequences obtained in this experiment are dependable and accurate.

Mentions:

Atkinson, J. , Burton, A. , Babson, M. , Hibert, C. , 2001. Advanced flat Chemistry A2. Heinemann Educational Publishers. Oxford.

Brumblay, R. U. , 1972. Quantitative Analysis. Barnes & A ; Noble. New York.

Christian, G. , 2003. Analytic Chemistry. 6Thursdayerectile dysfunction. Wiley and Sons. New York.

Hargis, L. , 1988. Analytic Chemistry: Principles and Techniques. Prentice Hall. New Jersey.

Nicholls, L. , 2001. Chemistry A2. 2neodymiumRevised Edition. HarperCollins Publishers, Inc. New York.

Nuffield Advanced Chemistry, 2006. Practical Investigations. hypertext transfer protocol: //www.chemistry-react.org/go/Topic/Default_4.html. [ Accessed: March 28, 2006 ] .

Wilbraham, A. Stanley D. , Matta, M. , 1997. Chemistry. 4Thursdayedition. Menlo Park, California: Addison-Wesley. ( pp.450-452 ) .

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