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What is the percent purity? |
sodium thiosulfate(Na2S2O3, molar mass=158.2g/mol) is used in photography. your summer job is at a photography lab, and you need to check the purity of an outdated supply. you find it takes 40.21 ml of 0.246 M iodine solution to react completely with a 3.232 g sample I2 + 2S2O3^(-2)----->2I^(-1) + S4O6^(-2) the answer is 96.8% how would you solve this? So you know that in this reaction you used up 40.21mL of 0.246M Iodine solution. That is 40.21mL*0.246mol/L, or 9.89167mmol of Iodine. In the reaction, each mol of iodine solution reactes with 2 mol of thiosulfate. This means that there must be twice as many mol of thiosulfate compared to iodine. Also, you know that each mol of thiosulfate comes from one mol of sodium thiosulfate. So, you have 9.98137mmol*2*158.2g/mol, which is 3.1297g of sodium thiosulfate. Then you divide the amount of actual sodium thiosulfate by the mass of your sample - 3.1297/3.232 is 96.8%! |
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