Unit 3: Chemical Kinetics Kinetics Summary

Kinetics Summary Worksheet 1. The diagram below shows the distribution of energies of molecules in a gas a certain temperature. (iii) Add a line showing the activation energy on the diagram and use it to help explain carefully how the diagram affords an explanation for the effect of increased temperature on a rate of reaction. Vertical line on right hand side of the graph. All particles to the right hand side of the line have sufficient energy for reaction, and therefore collisions between them result in a reaction (they are successful). The higher temperature curve has a greater number of particles that have sufficient energy for reaction (to the right of the line), so the rate of reaction is greater at a higher temperature

Kinetics Summary Worksheet 2. F and G react together. When the concentration of F is tripled and the concentration of G remains constant, there is a nine-fold increase in the rate of reaction. What is the order of reaction with respect to F? Second order 3. P and Q react to form E. In one experiment, the concentration of P is tripled while Q is kept constant. This causes the rate to triple. In a second experiment the concentration of Q is doubled while the concentration of P is kept constant. The rate is found to have quadrupled. Write a rate equation for this reaction. What is the overall order of reaction? Rate = k [P][Q]2 Overall order = 3

Kinetics Summary Worksheet 4. A reaction involves T as one of the reactants. Following the change in concentration of T over time yields the graph below. What does the graph tell us about the rate of reaction AND the order with respect to T? It is constant (constant slope), it is zero order with respect to T.

Kinetics Summary Worksheet 5. C decomposes to form D. The following results were obtained by experiment. What is the rate expression (equation)? What is the overall order of the reaction? Rate = k Overall order = zero order. Initial [C] in mol L-1 1.00 ´ 10-3 2.00 ´ 10-3 6.00 ´ 10-3 Rate in mol L-1 s-1 1.45 ´ 10-5

Kinetics Summary Worksheet 6. The reaction where A reacts with B to give P, is found to be first order with respect to both A and to B. When the initial concentrations of [A] = 3.30 ´ 10-6 mol L-1 & [B] = 2.85 ´ 10-3 mol L-1, the initial rate of reaction is 3.45 ´ 10-4 mol L-1 min-1. Calculate the rate constant for the reaction (include units). Rate = k [A][B] 3.45 ´ 10-4 mol L-1 min-1 = k (3.30 ´ 10-6 mol L-1 )(2.85 ´ 10-3 mol L-1) k = 36680 min-1 mol-1 L

Kinetics Summary Worksheet 7. In the reaction A + B ® Products the following results were obtained for the initial rates of reaction for different initial concentrations. Deduce the rate equation (explaining carefully how you reached your answer) and calculate the rate constant (include units). Rate = k [A][B] Experiment # [A] in M [B] in M Rate in M s-1 1 10 0.002 2 20 0.004 3 40 0.016

Kinetics Summary Worksheet 7. In the reaction A + B ® Products the following results were obtained for the initial rates of reaction for different initial concentrations. Deduce the rate equation (explaining carefully how you reached your answer) and calculate the rate constant (include units). First order with respect to A. Doubling A while keeping B constant causes the rate to double (Experiment #1 and #2) First order with respect to B. Consider experiments #2 and #3. Doubling A should result in a doubling of rate from 0.004 to 0.008 (since reaction is first order with respect to A). The rate actually doubles again to 0.016 due to the doubling of B, i.e. first order with respect to B Experiment # [A] in M [B] in M Rate in M s-1 1 10 0.002 2 20 0.004 3 40 0.016

Kinetics Summary Worksheet 8. What three criteria must be met if a reaction between two reactants is to take place? (i) Reactants must collide (ii) Reactants must collide with sufficient energy (activation energy) (iii) Reactants must collide with the correct collision geometry (orientation)