Name: ` Back to Blue Experiment Pre-lab Questions: Answer the questions below (3 marks) Common household bleach is an aqueous solution containing hypochlorite ions. A closed container of bleach is an equilibrium system represented by the equation below. Cl2(g) +2OH- (aq) ⇌ClO-(aq) + Cl- (aq) + H2O (l) 1. Compare the rate of the forward reaction to the rate of the reverse reaction for this system. 2. Explain why the container must be closed to maintain equilibrium. 3. State the effect on the concentration of the ClO- ion if there was a decrease in the concentration of the OH- ion. Name: ` Back to Blue Experiment Pre-lab Questions: Answer the questions below Common household bleach is an aqueous solution containing hypochlorite ions. A closed container of bleach is an equilibrium system represented by the equation below. (3 Marks) Cl2(g) +2OH- (aq) ⇌ClO-(aq) + Cl- (aq) + H2O (l) 1. Compare the rate of the forward reaction to the rate of the reverse reaction for this system. 2. Explain why the container must be closed to maintain equilibrium. 3. State the effect on the concentration of the ClO- ion if there was a decrease in the concentration of the OH- ion. Back to Blue Experiment /13 Name:__________________ Introduction: Over the past few lessons, we have talked about equilibrium and reversible reactions. Reversible reactions are a very common occurrence in chemical reactions and depending on what we do with these reactions will determine what is produced. This experiment will show us what a reversible reaction will look like. In addition, we will be able to see when a reaction reaches equilibrium and what happens if we put a stress on the system. Lastly, through Le Chatelier's principle, we will be able to predict what will happen to the reaction when we put different stresses on it. Note: It may be helpful to have a scarp piece of paper to record observations during the lab, which you can later use to complete your answers. Materials • graduated cylinder • 250 mL Erlenmeyer flask, • Weighing paper • Balance • Stirring rod • Stopper • Water • 1% methylene blue • 2.5g potassium hydroxide crystals, KOH(s) • 1.5g glucose, C6H12O6 • Timer Procedure/Observations: 1. Measure 125mL of water, pour into flask. Add 3 drops of methylene blue (teacher will add) 2. Measure 2.5g of potassium hydroxide onto weighing paper. Transfer to flask. 3. Measure and transfer 1.5g of glucose. 4. Stir the liquid with the stirring rod until all solid is dissolved. Put the stopper in and observe. 5. Holding the stopper in place, shake the solution vigorously. Place down and observe 6. Continue to observe the flask until another colour change occurs. Record observations 7. Test your solution for number of shakes vs. time to change. Record in the chart below. # of shakes Time to change colors (in seconds) Post- lab Questions: 1. What do you observe in the reaction above when you shake it? You can draw and/or highlight the important observations that you were able to see. (2 marks) 2. From the chart you completed, did you notice any trends between the shakes and the time to change colors? If so, what is it? In addition, what do you think is the reason for your trend? Explain your reasoning. (2 marks) 3. Why would this reaction be considered a reversible reaction? When does this reaction achieve equilibrium? Explain your reasoning based on your observations. (2 marks) 4. There are a few reactions to consider which we look at from a simplified standpoint: 1. C6H12O6 (s) + OH- (aq) ⇌ C6H11O6-(aq) + H2O (l) (This step supplies the reducer) Glucoside ion Glucose 2. O2 (g) ⇌O2 (aq) (this step supplies the oxidizer) Dissolved oxygen 3. Oxidized methylene blue ⇌ reduced methylene blue Blue colour Colourless a) What role does the KOH play in this experiment? (1 mark) b) By shaking the bottle, what did you do with the oxygen that causes the colour change? (1 mark)
