Question

1. A decomposition reaction has a half-life that is directly proportional to the initial concentration of the reactant. What is the order of the reaction?
2. Geologists can estimate the age of rocks by their uranium-238 content. The uranium is incorporated in the rock as it hardens and then decays with first-order kinetics and a half-life of 4.5 billion years. A rock is found to contain 83.4% of the amount of uranium-238 that it contained when it was formed. (The amount that the rock contained when it was formed can be deduced from the presence of the decay products of Geologists can estimate the age of rocks by their uranium-238 content. The uranium is incorporated in the rock as it hardens and then decays with first-order kinetics and a half-life of 4.5 billion years. A rock is found to contain 83.4% of the amount of uranium-238 that it contained when it was formed. (The amount that the rock contained when it was formed can be deduced from the presence of the decay products of U−238.) How old is the rock? How old is the rock in years?
3. These images represent the first order reaction These images represent the first order reaction At 400 K oxalic acid decomposes according to the reaction:

H2C2O4(g)→CO2(g)+HCOOH(g)

In three separate experiments, the intial pressure of oxalic acid and final total pressure after 20,000 s is measured.

Experiment 1 2 3

P H2C2O4 at t = 0 65.8 92.1 111

PTotal at t = 20,000 s 103 144 173

Find the rate law of the reaction.

4. Cyclopropane rearranges to form propene in the gas phaseCyclopropane rearranges to form propene in the gas phase. The reaction is first order in cyclopropane and has a measured rate constant of 3.36×10−5s−1 at 720 K.If the initial cyclopropane concetration is 0.0425 M , what is the cyclopropane concentration after 281 minutes?

Answer 1