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98 solutions

First Order Half Life

#### Q. Iodine-131 has a half-life of 8.1 days and is used as a tracer for the thyroid gland. If a patient drinks a sodium iodide (NaI) solution containing iodine-131, how many days will it take for the concentration of iodine-131 to drop to 5.0% of its initial concentration? A. 8.1 days. B. 16.2 days. C. 4.3 days. D. 35 days. E. 162 days

Solved • Feb 19, 2020

First Order Half Life

#### Q. What is the half-life of a first-order reaction with a rate constant of 7.90x10^-4 s^-1? Express your answer with the appropriate units.

Solved • Feb 11, 2020

First Order Half Life

#### Q. Half-life equation for first-order reactions: t1/2= 0.693/kwhere t1/2 is the half-life in seconds (s), and k is the rate constant in inverse seconds (s^-1). What is the rate constant of a first-order reaction that takes 350 seconds for the reactant concentration to drop to half its original value? Express your answer with the appropriate units.

Solved • Feb 6, 2020

First Order Half Life

#### Q. Half-life equation for first-order reactions: t1/2= 0.693/k where t1/2 is the half-life in seconds (s), and k is the rate constant in inverse seconds (s^-1). What is the rate constant of a first-order reaction that takes 454 seconds for the reactant concentration to drop to half of its initial value? Express your answer with the appropriate units.

Solved • Feb 13, 2020

First Order Half Life

#### Q. A radioactive isotope decays with a half life of 645s. How much of the material remains after 2 minutes?

Solved • Feb 14, 2020

First Order Half Life

#### Q. What is the half-life of methane in the atmosphere in years at 323 K? (Assume that [CH4]=[O3]=[A]0=5.0×10−7M). Explore what a half-life of methane means in the reaction and comment on the consequence of that in the atmosphere.

Solved • Feb 8, 2020

First Order Half Life

#### Q. The first-order rate constant for the decomposition of N2O5, 2N2O5 (g) → 4NO2 (g) + O2 (g) at 70 °C is 6.82x10^-3 s^-1. Suppose we start with 2.50x10^-2 mol of N2O5 (g) in a volume of 2.2 L.How many minutes will it take for the quantity of N2O5 to drop to 1.8x10^-2 mol? Express your answer using two significant figures.

Solved • Feb 10, 2020