Q3. Now consider the moment when the blue colour change is about to occur (i.e. when there is no more thiosulfate remaining in solution). Based on the initial experiment and initial concentrations of reagents, calculate the concentrations of the reagents present in the flask at the moment just before the blue colour change begins (ignore the starch, and the S4O62- which is formed as the other by-product in this reaction). Does Reaction (1) continue beyond this point? a. yes b. no Based on what you have calculated, which reagent in Reaction (1) is the limiting reagent? a. H+ b. H2O2 c. I- d. S2O32-

iodine is titrated with thiosulfate. What color change signals the endpoint?A.Green to blueB.Blue to greenC.Blue to clearD.Clear to blue

The equation for the reaction is 2 Na S2 O3 (aq) + 2HCl(aq) o 2NaCl(aq) + H2 O(l) + S(s) + SO2 (g) Before starting her experiments, the student considers the risk to her of sulfur dioxide escaping from the flask. She uses this information. concentration of sodium thiosulfate solution = 0.300 mol/dm3 volume of sodium thiosulfate solution = 20 cm3 volume of water = 20 cm3 volume of hydrochloric acid = 10 cm3 The solubility of sulfur dioxide at room temperature is 100 g/dm3. Use this additional information to explain whether any sulfur dioxide gas escapes from the flask.

(I)     (II) (III)     (IV) In which of the following beakers colour change of solution will take place after reaction?Only III and IIIOnly IVIII and IV

A chemist adds 1.90L of a 2.18/molL sodium thiosulfate Na2S2O3 solution to a reaction flask. Calculate the moles of sodium thiosulfate the chemist has added to the flask. Round your answer to 3 significant digits.

You are investigating how the rate of reaction depends upon the concentration of hydrochloric acid when it is reacted with sodium thiosulfate in a small glass beaker. Which reagent in this experiment poses the greatest hazard?sodium thiosulfatehydrochloric acid