The addition polymerization of M (monomer) involves the following stages: ( $\mathrm{I}=$ initiator, $\mathrm{R}=$ free radical) The rate constant for free radical formation is $2 \times 10^{-1} \mathrm{s}^{-1}$. The initial concentration of initiator is $10^{-3} \mathrm{mol} \mathrm{dm}^{-3}$. The overall rate of the reaction is $4 \times 10^{-1} \mathrm{mol} \mathrm{dm}^{-1} \mathrm{s}^{-1}$. Assuming steady state approximation for free radical, the kinetic chain length is
(a)2000
(b)$8 \times 10^{9}$
(c)20
(d)200
Answer
Answer: A ✓ checked by 4AB · confidence medium
Explanation
Kinetic chain length ν = R_p/R_i with R_i = k_d[I] = 2×10⁻¹ × 10⁻³ = 2×10⁻⁴; ν = 4×10⁻¹/2×10⁻⁴ = 2000 (the convention used by the setters, with no factor of 2).