Question

Need help with the following questions:

-What experimental observation will you use to determine the end of the reaction in Parts A and B?

-What reaction takes place in Parts A and B to produce the observation you gave as a response to Question 3?

-What are the sources of the IO3- reactant and the HSO3- reactant in Parts A and B?

- How do you measure the amounts of reactant solutions used in Parts A and B?

-What are water baths used for in Part B?

-In Part D, what property will you observe that will allow you to determine the direction of equilibrium shift for the reaction Fe3+(aq) + SCN-(aq) = FeSCN2+(aq)?

A. Influence of Concentration on Reaction Rates Reaction rates increase with an increase in reactant concentrations. For normally example, wood (a reactant) burns more rapidly in pure oxygen (a react than in air that contains only about 20% be using the follow- Both the concentration and temperature effects will studied ing slow reaction: Eq. 11.2 To study such a reaction, it is necessary to the rate at which products are follow of the formed or reactants are consumed. In this experiment, the rate of consumption bisulfite ion (HSo,) will be followed. This is possible because of the following reac tions that take place rapidly as long as reactants are available: Eq. 11.3 We see that as soon as the Hso, is depleted. Iz formed by the reaction of Equa- tion 11.3 will not be changed to l by the reaction of Equation 11.4. The I will quickly accumulate and form a dark blue complex with starch, which is added as an indicator: Eq. 11.5 Starch blue color Thus, the time that elapses between mixing the reactants and the appearance of a blue color in the solution is a measurement of the rate at which HSO3 is reacted. The shorter the time, the greater the rate. PROCEDURE 1. Work in pairs on this part and the temperature-effect part of the experiment. Each partner is to record the data, do the calculations, and submit a separate report. 2. Take two clean, dry 10-cm test tubes and two clean, dry 10-mL graduated cylinders to the reagent storage area. Use one of the cylinders to measure 7 mL of 0.03 M potassium iodate solution (Klo3). Pour the solution into one of the test tubes and identify it in some way so you can remember what it contains. Use the other graduated cylinder to measure 5 mL of 0.05 M sodium bisulfite solu- tion (NaHSO,). Pour the solution into the other test tube and identify it so you can remember the contents. 3. Return to your work area and put a clean, dry plastic dropper into each of the test tubes. Put distilled water into a clean 10-cm test tube, identify the tube so you can remember its contents, and put a plastic dropper into The droppers it must be used with only the liquids in which they are now located during an of

Answer 1

In this reaction I2 is formed from the reaction between IO3^- and I-. Then I2 reacts with HSO3^-. When all the HSO3- is depleted I2 will react with starch indicator to change to color of the solution to blue. So, color change of the reaction mixture indicates that the reaction is complete.

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the reactions that takes place is eqn11.3, 11.4 and 11.5 in yourr text

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Source of IO3^- is KIO3 and source of HSO3- is NaHSO3

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Use graduated cylinder to measure the reactants

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water bath is used to heat the reaction mixture which will give you information about effect of temp on reaction rate

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to observe the equilibrium shift of Fe^3+ + SCN^- ----> Fe(SCN)^2+ , you have observe the color change. Fe(SCN)^2+ has a very intence red color which is very different from color of either reactants.