Question

4. For the reaction A + 2B → C, the rate law is

Answer 1

The rate constant : b. 1/ M² · s

Further explanation  

The reaction rate (v) shows the change in the concentration of the substance (changes in addition to concentrations for reaction products or changes in concentration reduction for reactants) per unit time.  

For A + B  ---> C + D

Can be formulated:

$\large{\boxed{\boxed{\bold{v~=~k.[A]^a[B]^b}}}$

where

v = reaction speed, M / s

k = constant, mol¹⁻⁽ᵃ⁺ᵇ⁾. L⁽ᵃ⁺ᵇ⁾⁻¹. S⁻¹

a = reaction order to A

b = reaction order to B

[A] = [B] = concentration of substances

Units of the rate constant - k depend on rate law, so it is unique for the specific reaction

So for the rate law :

Δ[C]/ΔT = k[A]²[B] , the units are :

$\tt \dfrac{M}{s}=k\times M^2\times M\\\\k=\dfrac{M/s}{M^2\times M}\\\\k=\dfrac{1}{M^2.s}$