EXERCISE 1 NAME AB SECTIONDATE Questions 1. Why is it important that the concent
ID: 1032354 • Letter: E
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EXERCISE 1 NAME AB SECTIONDATE Questions 1. Why is it important that the concentration of hydroxide ion be much larger than the concentration of crystal violet? How would the analysis be different if the concentrations of both species were similar? 2. Suppose that the product of the reaction had the same absorption spectrum as the crystal violet Could you still use the procedure described here to run the experiment? Explain Suppose that the instrument overheated and the temperature of the cuvette were increased dur- ing the run. How would this affect the calculated rate constant and the shape of the graph? 3. 4. Suppose you made a mistake preparing the solution you used to determine e for crystal violet, and the concentration in the cuvette was two times higher than what you believed it to be. How would this affect your calculated value of e,m, n and k?Explanation / Answer
1. With the much higher concentration of the NaOH, the reaction rate is dependent only upon the concentraion of the limiting reactant crystal violet. If however, the concentration of both are the same, the reaction rate will now be dependent upon the concentration of both reactants. The rate of reaction will not remain first order. So to simplify the reaction kinetics, it is important to keep the concentration of NaOH to be much greater than crystal violet.
2. If both crystal violet and the product have the same absorption maxima, we cannot use the same experiment as before. The rate of change of crystal violet alone cannot be determined in this case as it will always be added with the product absorbance value. higher concentration of crystal violet will be observed in such a case, which is an error.
3. the rate constant would increase with increase in temperature. this is due to higher rate of reaction at higher temperature values. The shape of graph remains the same as at all temperatures the reaction follows first-order kinetics.
4. with higher concentration of crystal violet than expected. the absorbance would be higher, so e (molar absorpivity) value would also be much higher. similarly other values m and n will also be higher, whereas, k would remain the same.
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