First Order Rate Constant in Chemical Kinetics

Questions and Answers

A straight line (correct)

An exponential curve

A curved line

A hyperbolic curve

They are different for each reactant

They are equal to the reaction rate

They are unity (correct)

They are all zero

The reaction order increases proportionally

The reaction order remains the same

The reaction order can exceed 2 (correct)

The reaction order decreases

<p>The rate constant kA</p> Signup and view all the answers

<p>It indicates the change in concentration over time</p> Signup and view all the answers

Study Notes

A first-order reaction rate is dependent on the concentration of a single reactant (A).
The rate of change in the concentration of Z (dx/dt) is equal to kA (a0 - x), where kA is the first-order rate constant.
Integration of the rate equation yields -ln(a0 - x) = kAt - I, where I is the constant of integration.
The rate constant (kA) has units of s^-1.
A plot of ln[A] versus t is linear with a slope of -kA.

A second-order reaction rate is dependent on the product of the concentrations of two reactants (A and B).
The rate equation is r = kA (a0 - x)(b0 - x), where a0 and b0 are the initial concentrations of A and B.
Integration of the rate equation yields ln[b0(a0 - x)/a0(b0 - x)] = kAt.
A plot of 1/[A] versus time yields a straight line for a second-order reaction.

A zero-order reaction rate is independent of the concentration of reactants.
The rate equation is r = kA, where kA is the zero-order rate constant.
Integration of the rate equation yields x = kAt.
A plot of the product concentration versus time yields a straight line with a slope equal to the apparent zero-order rate constant.

Higher-order reactions are uncommon due to the low probability of simultaneous multiple body collisions.
Many rate laws incorporate multiple elementary reactions, resulting in a composite rate law with order >2.