AP 5.3 Concentration / Time BANK

What rate law matches the graph?

• rate= k [A]
• rate= k [A]²
• rate= k
• rate= k [A]³

What rate law matches the graph?

• rate= k [NO₂]
• rate= k [NO₂]²
• rate= k
• rate= k [NO₂]³

X → products

Pure substance X decomposes according to the equation above. Which of the following graphs indicates that the rate of decomposition is second order in X ?

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2 HO2 → H2O2+O2

The reaction represented by the chemical equation shown above occurs in Earth’s atmosphere. In an experiment, [HO2] was monitored over time and the data plotted as shown in the following graph.

Based on the information, which of the following is the rate law expression for the reaction?

• Rate=k

After a certain pesticide compound is applied to crops, its decomposition is a first-order reaction with a half-life of 56 days. What is the rate constant, k, for the decomposition reaction?

• 0.012/day

• 0.018/day

• 56/day

• 81/day

After a certain pesticide compound is applied to crops, its decomposition is a first-order reaction with a half-life of 32.5 days. What is the rate constant, k, for the decomposition reaction?

• 0.0213 /day

• 0.0308 /day

• 32.5 /day

• 46.9 /day

If the oxygen isotope ²⁰O has a half-life of 15 seconds, what fraction of a sample of pure ²⁰O remains after 1.0 minute?

• 1/2

• 1/4

• 7/30

• 1/8

• 1/16

The isomerization of cyclopropane to propylene is a first-order process with a half-life of 19 minutes at 500^oC. The time it takes for the partial pressure of cyclopropane to decrease from 1.0 atmosphere to 0.125 atmosphere at 500^oC is closest to

• 38 minutes

• 57 minutes

• 76 minutes

• 152 minutes

• 190 minutes

The rate constant (k) for the decay of the radioactive isotope I-131 is 3.6E−3 /hour. The slope of which of the following graphs is correct for the decay and could be used to confirm the value of k ?

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2 H₂O₂(aq) → 2 H₂O(l) + O₂(g)        ΔH° = −196 kJ/mol_rxn

The decomposition of H₂O₂(aq) is represented by the equation above. A student monitored the decomposition of a 1.0 L sample of H₂O₂(aq) at a constant temperature of 300. K and recorded the concentration of H₂O₂ as a function of time. The results are given in the table below.

Which of the following statements is a correct interpretation of the data regarding how the order of the reaction can be determined?

• The reaction must be first order because there is only one reactant species.

• The reaction is first order if the plot of ln [H₂O₂] versus time is a straight line.

• The reaction is first order if the plot of 1/[H₂O₂] versus time is a straight line.

• The reaction is second order because 2 is the coefficient of H₂O₂ in the chemical equation.