Bromine (0.05 M)
Molecular formula: Br2
Molecular weight: 159.81
Preparation: Dissolve 3 g of potassium bromate and 15 g of potassium bromide in sufficient water to produce 1000 mL.
Standardization: Pipette 25.0 mL of the solution into a 500 mL iodine flask and dilute with 120 mL of water. Add 5 mL of hydrochloric acid and insert the stopper in the flask and shake it gently. Add 5 mL of potassium iodide solution again insert the stopper and allow it to stand for 5 minutes in the dark. Titrate the liberated iodine with 0.1 M sodium thiosulphate using 3 mL of starch solution, added towards the end of the titration, as an indicator. Store the solution in dark amber-colored, glass stoppered bottles.
Br2 + S2O2−3 + H2O → 2Br + 2SO2−4 + 2H+
1 mole of Na2S2O3 ≅ 1 mole of bromine
1000 mL of 1M Na2S2O3 ≅ 159.81 g of Br2
1 mL of 0.1 M Na2S2O3 ≅ 0.01598 g of Br2
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