INTRODUCTION Many of the experiments performed in Chemistry 101 involved either the quantitative or qualitative analysis

[answerhappygod]

Introduction Many Of The Experiments Performed In Chemistry 101 Involved Either The Quantitative Or Qualitative Analysis 1 (117.82 KiB) Viewed 58 times

Introduction Many Of The Experiments Performed In Chemistry 101 Involved Either The Quantitative Or Qualitative Analysis 2 (21.27 KiB) Viewed 58 times

INTRODUCTION Many of the experiments performed in Chemistry 101 involved either the quantitative or qualitative analysis of a substance or solution. Another basic area of chemical research is the synthesis or preparation of either new or previously known compounds. In this experiment, a complex of iron (III) (Fe) and oxalate (C₂0,¹) is synthesized and precipitated as a salt (Fe, (C₂04), ³-2v). The preparation of iron (III) oxalate involves separate steps. First, iron (II) oxalate (note the different oxidation state of iron) is prepared by adding C₂O² to an acidic solution of Fe²*. Fe²(aq) + C₂0. (aq) → FeC₂0, (s) (1) FeC₂O₂ is a yellow solid. Hydrogen peroxide, H₂O₂, excess oxalate, and acid are then reacted with the yellow precipitate. The hydrogen peroxide oxidizes Fe²* to Fe³, and a green solution of the iron (III) oxalate ion results. A balanced chemical equation for this reaction may be written as: H* + x FeC₂O₂ (s) + ½ H₂O₂ + (y-x)C₂0₂² Fe(C₂04),³ + H₂O (2) The iron (III) oxalate ion is precipitated from solution as a salt by adding ethyl alcohol to the solution. The salt precipitates because its solubility in the alcohol/water solution is less than in pure water. PROCEDURE 1. Add 10 g of ferrous ammonium sulfate, Fe(NH4)2(SO4)2 6H₂0, 30 mL distilled water, and 6-8 drops of 6M H₂SO, to a 250 mL beaker. Support the beaker with a ring, wire screen, and ringstand. Using a Bunsesn burner, warm the solution until the ferrous ammonium sulfate is completely dissolved. Stir if necessary. 2. Stir the solution and add 50 mL of 1 M oxalic acid (H₂C₂O4) to the beaker. A yellow precipitate should form. 3. Carefully digest the mixture by heating the solution to boiling. Let the solution boil for about one minute. Avoid "bumping" of the solution by placing a clean stirring rod in the beaker. (Bumping is the violent splashing of solution and precipitates caused by the sudden evolution of large bubbles of vapor through the surface of the solution. A glass rod prevents the formation of large bubbles by providing a surface on which many small vapor bubbles may form. Digestion increases the size of the precipitate particles.) 4. Turn off the Bunsen burner and let the precipitate settle to the bottom of the beaker. 5. Carefully decant the liquid above the precipitate, leaving the precipitate in the beaker. 6. Wash the precipitate by adding 30 mL hot distilled water and stirring the solution. This step removes soluble impurities such as H, NHA", or SO, that may have adhered to the precipitate. Let the precipitate settle and decant the liquid. Repeat the washing once more. Decant the liquid. 7. Add 18 mL 2M potassium oxalate solution, K₂C₂O4, to the beaker. 8. Obtain a buret and thermometer from the stockroom. Fill the buret with about 25 mL of 6% H₂O₂ and support it using a ringstand and buret clamp. Slowly add, with constant stirring, 17 mL H₂O₂ to the beaker. DO NOT ALLOW THE TEMPERATURE TO GO ABOVE 55°C or unwanted side reactions may occur. Do NOT use your thermometer as a stirring rod (Why?). 9. Heat the mixture to boiling. While it is boiling, add 9 mL 1M H₂C₂O4 to the solution and then slowly add an additional 4 mL of 1M H₂C₂O4. Any rust brown precipitate of Fe(OH)3 that may have formed on the addition of H₂O₂ should dissolve. If the precipitate does not dissolve, slowly add an additional 2-5 mL 1M H₂C₂O4. If any solid residue remains, filter the solution using gravity filtration. Fold the filter paper as demonstrated by the instructor. Discard the residue. 10. Transfer the solution to a clean 150 mL beaker. Add 20 mL 95% ethyl alcohol. Cover with parafilm, label

Describe what was observed after each of the following procedures. Explain each observation based on the chemistry involved. Give a balanced chemical equation where possible. 1. Addition of 50 mL 1M H₂C₂O₂ (step 2) 2. Addition of 17 ml 6% H₂O₂ (step 8) 3. Addition of 13 mL 1M H₂C₂O₂ (step 9) 4. Filtration of the solution, if necessary (step 9) 5. Addition of 20mL 95% ethyl alcohol (step 10)