Question

In order to find the rate constant for a third order rate law, you should

(a)Take the slope of 1/ [A] vs time

(b)Take the slope of 1/ [A] vs temp

(c)Take the slope of Ln [A] vs time

(d)Take the slope of Ln [A] vs temp

(e)Use the rate law

Answer 1

The best way to identify fast and easy the rate of reaction AND the rate constant is via Graphical Method.

First, as the name implies, we need to graph all types of order (most common)

Zero = C vs t;

For zero order, there is no dependency of concentrations:

dC/dt = k*C^0

dC/dt = k

When developed:

C = C0 - kt

if x axis is "time" then the slope is "k", and y-intercept is initial concentration C0. y-axis if C (concentration)

First = ln(C) vs. t

For first order

dC/dt = k*C^1

dC/dt = k*C

When developed:

dC/C = k*dt

ln(C) = ln(C0) - kt

if x axis is "time" then the slope is "-k", and y-intercept is initial concentration C0. y-axis if ln(C) (natural logarithm of concentration)

Second = 1/C vs. t

For Second order

dC/dt = k*C^2

When developed:

dC/C^2 = k*dt

1/C= 1/C0 + kt

if x axis is "time" then the slope is "k", and y-intercept is initial concentration C0. y-axis if 1/(C (inverse of concentration)

Third = 1/C2 vs. t

For Thirdorder

dC/dt = k*C^3

When developed:

dC/C^3 = k*dt

1/C^2= 1/C0^2 + kt

then, we need to

there is no option shown

therefore, the best thing to do is

(e)Use the rate law

that is, get 1 point, substitute

Rate = k*[A]^3

rate, and concentration of A

k = Rate/[A]^3

solve for k, then you rill get k