A tree killed by being buried under volcanic ash was found to have a ratio of carbon-14 atoms to carbon-12 atoms of 4.3 × 10-14. The rate constant of the C-14 → C-12 decay is k = 1.21 × 10-4 yr-1 and the ratio of carbon-14 to carbon-12 is 1.2 × 10-12 in a contemporary sample.

Hydrogen sulfide burns in oxygen to form sulfur dioxide and water. If sulfur dioxide is being formed at a rate of 0.43 mol L-1 s-1, what are the rates of disappearance of hydrogen sulfide and oxygen?

The decomposition of N2O5 has an activation energy of 103 kJ/mol and a frequency factor of 4.3 × 1013 s-1. What is the rate constant for this decomposition at 25 celsius and 373 K

The decomposition of urea, (NH2)2CO, in 0.10 M HCl follows the equation
(NH2)2CO(aq) + 2H+(aq) + H2O 2NH4+(aq) + CO2(g)
At 65°C, k = 5.84 × 10-6 min-1 and at 75°C, k = 2.25 × 10-5 min-1. If this reaction is run at 85°C starting with a urea concentration of 0.0087 M, how many minutes will it take for the urea concentration to drop to 0.0012 M?

If it takes 78.7 min for the concentration of a reactant to drop to 20.0% of its initial value in a first-order reaction, what is the rate constant for the reaction in the units min-1?

The decomposition of acetaldehyde, CH3CHO, was determined to be a second order reaction with a rate constant of 0.0771 M-1 s-1. If the initial concentration of acetaldehyde is 0.225 M , what will the concentration be after selected reaction times? after 30 min? after 180 min?