<p>Chemistry Name Period The Reaction Rates Activity</p><p>Background How does the concentration of reactants influence the rate of a chemical reaction? In this experiment you will investigate the role of this variable on the rate of a chemical reaction that takes time before the reaction is completely over. This interesting reaction, called a “clock reaction”, allows us to time how long a series of chemical reactions takes in order to make a colorful product.</p><p>Purpose To show quantitatively the influence of concentration on the time required for a reaction (and therefore influence the reaction rate).</p><p>The clock reaction is performed by mixing these two solutions: - 1. Solution A is starch and another reactant, hydrogen sulfite ion, HSO3 (aq). 2. Solution B is a dilute solution of potassium iodate, KIO3. This is the source of the iodate ion, - IO3 (aq).</p><p>When these two solutions are thoroughly mixed, the ions of the resulting solution proceed through the following reactions according to your flow chart below them:</p><p>- - - -2 + 1. 3 HSO3 (aq) + IO3 (aq) I (aq) + 3 SO4 (aq) + 3 H (aq) solution A solution B</p><p>- + - 2. 5 I (aq) + 6 H (aq) + IO3 (aq) 3 I2 (dissolved) + 3 H2O (I)</p><p>- - -2 + 3. I2 (dissolved) + HSO3 (aq) + H2O (I) 2 I (aq) + SO4 (aq) + 3H (aq)</p><p>4. I2 (dissolved) + starch blue solution </p><p>The reactions take place in the manner outlined in the flow chart below. Only when the - HSO3 (aq) has been entirely consumed in reactions 1, 2, and 3, will the I2 (dissolved) react with - the starch on reaction 4. The appearance of the blue color indicates tha t all the HSO3 (aq) has been consumed and I2 remains in the solution. The dissolved I2 reacts with the starch to make the blue color. Reaction 4</p><p>Is any Mix Reaction Reaction Reaction HSO - 1 2 3 Solutions 3 left?</p><p>Note: The dilutions you will be making for this activity are not measured volumes of milliliters, rather they are made with drops using plastic bulb pipets. Make your dilution calculations using “drops” as units for volume. Example for Reaction 2: (0.020 M) (8 drops) = (M2) (10 drops) Procedure: The Effect of Concentration Changes 1. Prepare the reaction combination (1 to 5) that you are given in your spot well plate. 2. First add the drops of solution B, then add the drops of water (if required), then add the 10 drops of solution A last . Using the stopwatch, start timing when the first drop of solution A hits solution B in the spot well plate. Stop the stopwatch at the first sign of a reaction. 3. Repeat the experiment a second time and provide your average reaction time value for class data. 4. Use room temperature for temperature of the reaction.</p><p>Class Reactants: Concentration Avg. Temperature Average of KIO3 Reaction Reaction: Reaction solution B (+ H2O)+ (solution B) Time ( ) Time solution A ( ) ( ) ( )</p><p>10 drops solution B 1. + 10 drops solution A</p><p>8 drops solution B 2. + 2 drops of H2O + 10 drops solution A 6 drops solution B 3. + 4 drops of H2O + 10 drops solution A 4 drops solution B 4. + 6 drops of H2O + 10 drops solution A 2 drops solution B 5. + 8 drops of H2O + 10 drops solution A</p><p>Graph 1-1: Concentration of KIO3 (x) vs. Time (y)</p><p>Conclusion: 1. Explain the “clock reaction” for this laboratory and include the effect of the concentration on the reaction you observed.</p><p>2. One Chunk: What is the relationship between concentration and time of reaction? What is the relationship between concentration and rate of the reaction?</p><p>Error Analysis: 1. What errors may explain data that does not fall on the line of your graph when the concentration of solution B decreases?</p>