Chemical Kinetics quiz

The unit of rate constant for a first order reaction is:

The half-life of a first order reaction is:

For a zero order reaction, a plot of [R] versus t is a straight line with slope:

Molecularity of a reaction can be:

A catalyst increases the rate of a reaction by:

If the half-life of a first order reaction is 30 minutes, the time for 87.5% completion is:

In the Arrhenius equation k = A e^(-Ea/RT), A is called the:

Acid hydrolysis of ethyl acetate is an example of:

For a reaction, rate = k[A]^2[B]. If the concentration of A is doubled, the rate becomes:

A plot of log k versus 1/T has a slope equal to:

State two factors that affect the rate of a reaction. (2 marks)

What is meant by the rate law? How is it different from the law of mass action? (2 marks)

Derive the units of the rate constant for a second order reaction. (2 marks)

Why does the rate of a reaction generally increase with temperature? (2 marks)

Give one example each of a zero order and a first order reaction. (2 marks)

What is an elementary reaction? How is its order related to molecularity? (2 marks)

For a reaction R -> P, the concentration of R falls from 0.03 M to 0.02 M in 25 minutes. Calculate the average rate in M per minute and M per second. (2 marks)

What is the effective collision in collision theory? (2 marks)

Why is molecularity not applicable to complex reactions? (2 marks)

Show that for a zero order reaction t1/2 = [R]0/2k. (2 marks)

A first order reaction is 20% complete in 10 minutes. Calculate the rate constant and the half-life (log 1.25 = 0.0969). (3 marks)

The half-life of a radioactive isotope (first order) is 30 days. Calculate the fraction remaining after 90 days, and the rate constant. (3 marks)

The activation energy of a reaction is 52.9 kJ/mol. By what factor does the rate constant increase when the temperature rises from 300 K to 310 K? (Use log(k2/k1) = (Ea/2.303R)(T2 - T1)/(T1 T2), R = 8.314 J K^-1 mol^-1; antilog 0.297 = 1.98.) (3 marks)

For a first order reaction, calculate the ratio of the time required for 99% completion to the time required for 90% completion. (3 marks)

A reaction is second order with respect to a reactant. How does the rate change if the concentration of the reactant is (i) doubled (ii) reduced to half? Calculate the rate constant if the rate is 0.004 M/s at a concentration of 0.2 M. (3 marks)

Read the passage and answer the questions. In a hospital, the radioactive isotope iodine-131, which has a half-life of about 8 days, is used to treat thyroid disorders. A patient receives a dose of 80 units. Radioactive decay follows first order kinetics. (i) Calculate the rate constant. (ii) How much will remain after 24 days? (iii) Why is the half-life independent of the dose given? (5 marks)

Read the passage and answer the questions. Milk kept at room temperature (about 300 K) turns sour in about 8 hours, but in a refrigerator at about 277 K it stays fresh for much longer. Food scientists explain this using the temperature dependence of reaction rates. (i) Why does milk spoil more slowly in the refrigerator? (ii) Name the equation that relates rate constant and temperature. (iii) What does a high activation energy mean for the sensitivity of rate to temperature? (5 marks)

Read the passage and answer the questions. In the decomposition of ammonia on a hot platinum surface, the rate remains constant even when the pressure of ammonia is increased, because the surface becomes fully covered. (i) What is the order of this reaction? (ii) Write its rate law and the unit of k. (iii) Write the integrated rate equation for this order. (5 marks)

Read the passage and answer the questions. Inversion of cane sugar in the presence of acid follows the rate law rate = k[C12H22O11], although water is also a reactant. Water is present in large excess. (i) What type of reaction is this? (ii) Why does the concentration of water not appear in the rate law? (iii) What is its molecularity? (5 marks)

Read the passage and answer the questions. A catalytic converter in a car uses platinum and rhodium to convert harmful CO and NO into CO2 and N2 at a much faster rate. The catalyst is not consumed. (i) How does the catalyst increase the rate? (ii) Does the catalyst change the equilibrium constant? Explain. (iii) Draw the energy profile diagram with and without the catalyst. (5 marks)

Derive the integrated rate equation for a first order reaction. Draw graphs of [R] versus t and log[R] versus t, and derive the expression for half-life. (6 marks)

Derive the integrated rate equation for a zero order reaction and draw the relevant graphs. Give two examples of zero order reactions. (6 marks)

Explain the Arrhenius equation and the effect of temperature on rate. Draw the energy distribution curves at two temperatures and the plot of ln k versus 1/T. (6 marks)

Explain the role of a catalyst in a chemical reaction with an energy profile diagram, and describe collision theory and its limitations. (6 marks)

Explain the methods to determine the order of a reaction from experimental data. Using your own example of initial rate data, derive a rate law and calculate the rate constant. (6 marks)