gistfile1.txt

Reaction Rates

Reaction Rates

 

 

Introduction:

 

Many factors affect the rate of a chemical reaction. In this exercise you will examine how changes in concentration, temperature, particle size, and the addition of a catalyst alter reaction rates.

 

Part 1:  You will change the concentration of one reagent  while maintaining a constant temperature to determine how the concentration affects reaction rate. 

 

Part 2:  You will change the temperature of the reaction while the concentration remains constant to determine it's affect on reaction rate.

 

Part 3:  You will change the particle size of the reagent to determine it's affect on reaction rate.

 

Part 4:  You will observe a reaction without a catalyst and with a catalyst and also quantitatively measure the mass of the catalyst before and after the reaction.

 

Following your investigations, answer all questions and plot all graphs in the data analysis section and from this conclude the relationship between reaction rate and each of the four factors.  You may find it useful to read the Analysis and Questions before starting the lab.

 

Materials List:

 

Parts 1 and 2:

            Solution A : Potassium iodate, KIO3                                

            Solution B : starch and bisulfite ion, HSO3 -                            

            Distilled water

 

Part 3:                                   

            flour

 

Part 4:

            3% hydrogen peroxide

            manganese dioxide

 

 

 

Instructions :

 

 

Part 1: Reagent Concentration and Reaction Rate

 

1. Obtain 2 100 ml beakers. Label one Solution A and one Solution B.

 

Fill Sol. A beaker half full with Sol. A for Part 1

Fill Sol. B beaker half full with Sol. B

 

2. Measure 10.0 ml of Sol. A in a 10.0 ml graduated cylinder and pour it into a large test tube.

 

3. Measure 10.0 ml of Sol. B in a second 10.0 ml graduated cylinder and pour it into a second large test tube.

 

4. Mix the two solutions in the test tubes by pouring one into the other three times.

 

5. Begin timing the reaction, in seconds, as soon as the two solutions touch.

            Stop timing as soon as the whole solution turns blue.

 

6. Repeat the above process using the following dilutions to Sol. A.              

            Sol. B does not get diluted, use the same amount of Sol. B.

 

            Volume of Sol. A              Volume of Distilled Water             Volume of Sol. B

                     8.0                                                        2.0                                 10

                     6.0                                                        4.0                                 10

                     4.0                                                        6.0                                 10

                     2.0                                                        8.0                                 10

 

        Prepare the dilutions by first measuring Sol. A in its graduated cylinder and then add the water to the 10.0 ml mark. Rinse out the graduated cylinder each time between dilutions.

 

 

 

Part 2: Temperature and Reaction Rate

    

        In this part, each pair will be assigned a temperature at which they are to perform the reaction.

 

 

1. Get a new 100 ml beaker for Sol. A and use the same Sol. B beaker from part 1.

 

    Fill Sol.A beaker half full with sol. A for Part 2

    Fill Sol. B beaker half full with sol. B

 

2. Obtain 4 large test tubes, label two as Sol. A and two as Sol. B

    To two of the tubes add 10.0 ml of Sol. A to each.

    To two of the tubes add 10.0 ml of Sol. B to each.

 

3. Place the four test tubes in a large beaker filled with a water at your assigned temperature. You must manitian this temp while the tubes sit in this water bath for ten minutes.

 

4. Take the temp of the bath after the 10 miuntes and then mix Sol. A and Sol. B and time in the same fashion as Part 1.  Immediately after mixing place the tube with the mixed solution back into the water bath.

5. Repeat step 4 for the remaining two tubes.

 

6. Record both of your times and the average time on the date table for the class.

 

CLEAN UP for Part 1 and 2:

     Discard all reaction mixtures and unused solutions down the drain and wash all

glass ware with hot soapy water and rinse well !

 

 

 

Part 3: Particle Size and Reaction Rate

 

1. Pile flour on a watch glass and light the pile with a match. Observe.

 

2. Scoop up some of the flour with a spatula and sprinkle the flour into a lit burner. Observe.

 

CLEAN UP:  Discard all unused flour and wipe up any residue.

 

 

 

Part 4: Catalysts and Reaction Rate

 

1. Weigh out 0.50 g of maganese dioxide and record.

 

2.  Measure 100 ml of hydrogen peroxide and place it into a flask.

 

3.  Observe the hydrogen peroxide uncatalyzed.

 

4.  Drop the manganese dioxide into the flask and stand back.

 

 

CLEAN UP:  Return the manganese dioxide to your instructor and discard the contents of the flask.

 

 

 

Analysis:

 

1. Calculate the concentration of Sol A in Part 1 for each dilution done.

                               Initial Conc. of Sol A = .020 M

 

      Conc. of Sol A  = ( Initial Concentration )( Vol. of Sol A used )

                                       (Total Volume of mixed solutions)

 

2. Plot a graph of Reaction Time  vs.  Conc. of Sol. A

 

3. Plot a graph of 1/ Reaction Time ( reaction rate )  vs. Conc. of Sol. A

 

4. Plot a graph of Reaction Time vs. Temp.

 

Questions :

 

1. What happens to the reaction time as the Sol. A concentration increases ?                                                               State the mathematical relationship.

 

2. What happens to the reaction rate as the Sol. A concentration increases ?

                            State the mathematical relationship.

 

3. What happens to reaction time as the temperature increases ?

                             State the mathematical relationship.

 

4. What happens to reaction rate as the temperature increases ?

                              State the mathematical relationship.

 

5. What is the relationship between reaction time and reaction rate ? 

                                Explain.

 

6. What is the relationship between particle size and reaction rate ?

                                Explain.

 

7. Calculate % recovery of the catalyst in Part 4 and then write the equation for the reaction and draw the energy profile curves for the uncatalyzed and catalyzed reactions.

 

8. What is the relationship between catalysts and reaction rate ?

                                 Explain

 

9.  State conclusions for each part.