Chem 20L Essa
2
In chemical kinetics, the rate law describes the relation between the reaction rate and the concentration of the reactants in a chemical reaction. In this assignment, we look at the rate law for the reaction 2A + 2B -> C + D. For a reaction between two reactants with concentrations of [A] and [B], the rate law is given by the following equation: Rate = k[A]^m[B]^n. K represents the rate constant while the reaction orders of A and B are given by m and n, which are determined experimentally. These reaction orders are determined by observing the change in the instantaneous initial rate as we vary the concentrations of A and B strategically. For example, we can determine the reaction order of A by seeing how the instantaneous initial rate changes as we change the concentration of A while keeping the concentration of B constant. After finding the reaction orders, we can calculate the rate constant using the experimental data. In this assignment, we are given the data for four different trials in which we are given the concentrations of A, B, and the instantaneous initial rate. Looking at the data from trials one and two, we can observe that the instantaneous initial rate doubles as the concentration of B is doubled while that of A is kept constant. Since the concentration of B is directly proportional to the instantaneous initial rate, we can determine that the reaction order of B is one and the plot ln[B] vs. time would yield a straight line. Next, we look at trials one and three, in which the concentration of B is kept constant. As the concentration of A is doubled, the instantaneous initial rate quadruples. Therefore, we can determine that the reaction order of A is two and the plot 1/[A] vs. time would yield a straight line. Adding up the reaction orders of A and B, we calculate the overall reaction order to be three. Based on the rate law, we determine the reaction considered not to be an elementary reaction since the reaction order of B does not equal to its coefficient in the balanced reaction shown above. Finding the reaction orders of A and B, we can now write the new equation, rate = k[A]^2[B], which can rewritten as k = rate/([A]^2[B]). Plugging in the values of instantaneous initial rate and concentrations of A and B, we calculate the rate constant k. Solving for k in each trial, we find k1, k2, k3, and k4 to equal 0.103 M^-2 s^-1. Since the rate constant is the same for each trial, the average rate constant is also 0.103 M^-2 s^-1.
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Transcript of Chem 20L Essa
In chemical kinetics, the rate law describes the relation between the reaction rate and the concentration of the reactants in a chemical reaction. In this assignment, we look at the rate law for the reaction 2A + 2B -> C + D. For a reaction between two reactants with concentrations of [A] and [B], the rate law is given by the following equation: Rate = k[A]^m[B]^n. K represents the rate constant while the reaction orders of A and B are given by m and n, which are determined experimentally. These reaction orders are determined by observing the change in the instantaneous initial rate as we vary the concentrations of A and B strategically. For example, we can determine the reaction order of A by seeing how the instantaneous initial rate changes as we change the concentration of A while keeping the concentration of B constant. After finding the reaction orders, we can calculate the rate constant using the experimental data.In this assignment, we are given the data for four different trials in which we are given the concentrations of A, B, and the instantaneous initial rate. Looking at the data from trials one and two, we can observe that the instantaneous initial rate doubles as the concentration of B is doubled while that of A is kept constant. Since the concentration of B is directly proportional to the instantaneous initial rate, we can determine that the reaction order of B is one and the plot ln[B] vs. time would yield a straight line. Next, we look at trials one and three, in which the concentration of B is kept constant. As the concentration of A is doubled, the instantaneous initial rate quadruples. Therefore, we can determine that the reaction order of A is two and the plot 1/[A] vs. time would yield a straight line. Adding up the reaction orders of A and B, we calculate the overall reaction order to be three. Based on the rate law, we determine the reaction considered not to be an elementary reaction since the reaction order of B does not equal to its coefficient in the balanced reaction shown above.Finding the reaction orders of A and B, we can now write the new equation, rate = k[A]^2[B], which can rewritten as k = rate/([A]^2[B]). Plugging in the values of instantaneous initial rate and concentrations of A and B, we calculate the rate constant k. Solving for k in each trial, we find k1, k2, k3, and k4 to equal 0.103 M^-2 s^-1. Since the rate constant is the same for each trial, the average rate constant is also 0.103 M^-2 s^-1.In summary, we determined the rate law for the reaction 2A + 2B -> C + D by first finding the reaction orders of A and B. Using the instantaneous initial rates and concentrations given in the data provided, we found the rate constant k for each trial, which averaged to equal 0.103 M^-2 s^-1. Putting everything together, we can write the final rate law equation, Rate = (0.103 M^-2 s^-1)[A]^2[B].
