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# Reactions, Concentration, Half-Life, and Activation Energies

Please explain each step and label what each variable in an equation stands for. This class is second half of first year general chem so please to not get too advanced. Thanks

Average Rate of Reaction. The initial concentration of butyl chloride is 0.1000 M. What is the average rate of reaction if the chemical reaction below takes place, decreasing [butyl chloride] from 0.0905 M at time = 50.0 seconds to 0.0741 M at time = 150.0 seconds?
C4H9Cl(aq) + H2O(l) &#61614; C4H9OH(aq) + HCl(aq)

The Concentration-Time Equation. The first-order rate constant for the decomposition of an insecticide in water at 12°C is 1.45 1/yr. A quantity of this insecticide is washed into a lake on June 1, leading to a concentration of 5.0 x 10-7 g/cm3 of water. Assume that the effective temperature of the lake is 12°C. &#61569; What is the concentration of the insecticide on June 1 of the following year? &#61570; How long will it take for the concentration of the insecticide to decrease to 3.0 x 10-7 g/cm3?

Half-Life of a Reaction. Consider the following reaction at 300°C: NO2(g) ---> NO(g) + ½ O2(g).

Describe what kinds of plots you would have to construct to determine if the reaction is first-order or second-order. What would these plots look like and how would they allow you to determine the order of the reaction? If the rate constant for the reaction at 300°C is found to be 0.543 M -1s-1, what is the half-life for the decomposition of NO2 if [NO2]o = 0.0100 M?

Activation Energy. Use the data below to answer the following questions about a chemical reaction. &#61569; What is the activation energy for the chemical reaction. &#61570; What is the value of the rate constant at 430.0 K?

Temperature (°C) k (1/s)
189.7 2.52 x 10-5
198.9 5.25 x 10-5
230.3 6.30 x 10-4
251.2 3.16 x 10-3

#### Solution Summary

The solution covers a number of general chemistry concepts, including average rate of reaction, the concentration-time equation, half-life of reaction, and activation energy. Detailed explanations are given along with sample calculations.

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