activity 13 chem lab

• chemicals needed in activity 13: sodium lauryl sulfate(SLS), HNO3, 0.1 N AgNO3 VS, potassium chromate (K2CrO4)
• title of activity 13: ASSAY OF SODIUM LAURYL SULFATE FOR SODIUM CHLORIDE CONTENT
• ACT 13.

  1. dissolve about 2 g SLS , accurately weighed ,in about 20 ml of water
• act 13 2. neutralize the solution with diluted HNO3 (1:20), using litmus paper as the indicator
• act 13

  3. Add 2 mL of K2CrO4 T.S
• act 13

  5. Titrate with 0.1 N AgNO3 until there is a formation of red precipitates.
• Why should standard solution of AgNO3 be protected from light? How?

  since AgNO3 is photosensitive,this means light triggers decomposition. when exposed to light ,agno3 breaks down into silver oxide and nitric acid.
• What are the different types of precipitation method of analysis? Describe each

  1. mohr method - determines the chloride ion concentration of asolution by titration with silver nitrate .
  2. fajans method- uses the reaction between precipitate formed and indicator. the indicator used is dichlorofluorescein which acts as an anion in solution
  3. volhards method - this method involves titration of bromides ,iodides, and chlorides,in acidic medium
• title of activity 14

  Preparation and Standardization of 0.1 N Iodine Solution
• Chemicals Needed in act. 14 :

  Iodine (I2)

  NaHCO3

  Potassium Iodide (KI)

  Starch T.S.

  Arsenic Trioxide (As2O3)

  Methyl Orange solution

  1 N NaOH

  Diluted HCl
• act 14.

  Procedure:

  A. Preparatiom

  1. Dissolve about 3.5 g of I2 in a solution of 9 g of KI in 30 mL of water.
  2. Add 3 drops of diluted HCl.
  3. 3. Add sufficient amount of water to make 250 mL.
• ACT 14

  B. Standardization

  1. Weigh accurately about 100-150 mg of As2O3, previously dried at 105°C for 1 hour. Transfer to a 500-mL erlenmeyer flask.
  2. Dissolve in 20 mL of 1 N NaOH. Warm the solution of necessary.
  3. Dilute with 40 mL water.
  4. Add 2 drops of methyl orange solution.
  5. Add diluted HCl drop by drop until the solution turns yellow to pink.
  6. Add 2 g of NaHCO3.
  7. Dilute with 50 mL water.
  8. Add 3 mL starch T.S.
  9. Titrate with I2 solution from a buret until a permanent blue color solution is produced.