How do you make a 0.05 M solution of iodine?

Iodine (0.05 M) 

Molecular formula: I2 

Molecular weight: 126.90 

Preparation: Dissolve about 14 g of iodine in a solution of 36 g of potassium iodide in  100 mL of water, add three drops of hydrochloric acid and dilute with water to 1000 mL. 

Standardization: Weigh accurately about 0.15 g of arsenic trioxide, previously dried at  105 oC for 1 hour, and dissolve in 20 mL of 1 M sodium hydroxide by warming, if necessary.  Dilute with 40 mL of water, add 0.1 mL of methyl orange solution and add drop-wise dilute hydrochloric acid until the yellow colour is changed to pink. 

Add 2 g of sodium carbonate dilute with 50 mL of water and add 3 mL of starch solution.  Titrate with the iodine solution until a permanent blue colour is produced. Store the solution in amber-coloured, glass stoppered bottles. 


As2O3 + 2I2 + 5H2O → 2AsO3−4 + 4I + 10H+ 

As2O3 + 6NaOH → 2Na3AsO3 + 3H2

Na3AsO3 + I2 + H2O → Na3AsO4 + 2I+ 2H+ 

Starch + I2 → Starch-Iodine  (blue colour) 

Factor Calculation: 

2 moles of I2 ≅ 1 mole of arsenic trioxide 

2000 mL of 1M I2 ≅ 197.84 g of AS2O3 

1 mL of 0.05M iodine ≅ 0.004946 g of As2O3

Make sure you also check our other amazing Article on: How do you make 0.1 M sodium thiosulphate solution?
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