Question

1. The rate law for the reaction is:
Cl2(g) + CHCl3 (g) = HCl (g) + CCl4 (g)
Is
Rate = k [Cl2]^1/2 [CHCl3]

What are the units for k, assuming time inow seconds and concentration in mol/L

2. What is the unit for the rate of a chemical reaction and the rate constant for a third-order rate law?

Answer 1

1. Given reaction is Cl2(g)+CHCl3(g)=HCl(g)+CCl4(g)

Rate=k[Cl2]^1/2[CHCl3]

We know that rate units => mol/L/ per second or M/s (as M=n/V)

and Unit for [Cl2]=M and [CHCl3]=M

Therefore substitute in above equation

mol/L/s = k [(M)^0.5 x M]

mol/L/s = k [(mol/L)^1.5]

k=(mol/L/s)/(mol/L)^1.5

The units for rate constant k=(mol/L)^-0.5 s^-1 =mol^-0.5 L^0.5.s^-1.

2. The rate of 3rd order reaction is

Rate=k[A]³

The rate of reaction is 3.

The units for rate constant

mol/L/s=k[mol/L]³

k=(mol/L/s)/(mol/L)³

k=mol^-2.L².s^-1.