Rate Constant
Definition
The rate constant (k) is a proportionality factor in kinetics equations that relates the rate of a reaction to the concentrations of reactants. Its value depends on temperature and other factors but not on concentration.
Analogy
Consider baking cookies in an oven set at 350 degrees Fahrenheit. No matter how many cookies you put inside, they will all bake at roughly the same pace because 350 degrees is our constant temperature, just as k is our constant for reactions under specific conditions.
Related terms
First-Order Reaction: A type of reaction where its rate depends on one reactant’s concentration raised to power one, much like baking one batch (or "order") of cookies would depend on having enough dough for that single batch.
Arrhenius Equation: An equation that shows how temperature affects reaction rates and thus impacts k, similar to how changing your oven's temperature would affect cookie-baking times.
Half-Life (t1/2): The time required for the concentration of a reactant to decrease to half its initial value. It's like if you started eating your cookies at a constant rate, the half-life would be the time it takes for half of them to disappear.
"Rate Constant" appears in:
Study guides (4)
Practice Questions (8)
- A reaction is represented by the equation XA -> X + A. At a certain temperature, the rate constant is 2.5 1/M·s. What is the rate of the reaction if the initial [XA] = 1.1 M?
- What is the unit of the rate constant of a reaction that has an overall order of 2?
- The rate law for the following reaction is R = k[XY]^2. The initial rate of the reaction was found to be 0.16 mol/Ls when the initial concentration of XY is 0.40 mol/L. What is the value of the rate constant, k?
- The rate law for the following reaction is R = k[A]^2. The initial rate of the reaction is defined as 0.080 mol/Ls, whereas the initial concentration of X is 0.20 mol/L. What is the value of the rate constant, k, for this reaction?
- In a first order reaction, a rate constant of 0.33 min^-1 is present. It will take how many minutes for the concentration to decrease from 0.13 M to 0.088 M?
- The rate constant for a second-order reaction is 0.13 M^-1*s^-1. While the inital concentration of reactant comes to 0.26 mol/L, it will take how many seconds for it to decrease to 0.13 mol/L?
- The decomposition of a pestecide compound applied to crops results in a first-order reaction with 56 days as its half-life. What is the rate constant?
- The value of the rate constant will ___________ as the temperature increases.
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