A solution of Na2S2O3 is standardized iodimetrically against 0.1262 g of KBrO3. This process requires 45ml of the Na2S2O3 solution. What is the molarity of the Na2S2O3?
A
0.2M
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B
0.01M
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C
0.05M
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D
0.1M
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Solution
The correct option is B0.01M The balanced chemical equation is as shown below: 8Na2S2O3+10KBrO3+7H2SO4→Na2S4O6+5K2SO4+14NaHSO4+5Br2 The number of millimoles of KBrO3 present in 0.1262 g is 0.1267167×1000=0.7555. The number of millimoles of Na2S2O3 required for the titration is 0.7555×810=0.6044. The volume of Na2S2O3 solution is 45 ml. The molarity of Na2S2O3 solution is 0.604445=0.013≃0.01M.