Define the following terms:
$(1)$ Elementary reaction
$(2)$ Complex reaction

For the reaction $Cl_{2(aq)} + H_2S_{(aq)} \to S_{(s)} + 2H^+_{(aq)} + 2Cl^-_{(aq)}$, the rate law is given by $\text{Rate} = K[Cl_2][H_2S]$. Which of the following mechanisms is consistent with this rate law?
$(A)$ $Cl_2 + H_2S \to H^+ + Cl^- + Cl^+ + HS^-$ (slow); $Cl^+ + HS^- \to H^+ + Cl^- + S$ (fast)
$(B)$ $H_2S \rightleftharpoons H^+ + HS^-$ (fast equilibrium); $Cl_2 + HS^- \to 2Cl^- + H^+ + S$ (slow)

........ of a reaction cannot be determined experimentally.

The numerical values of rate constants are same for first,second and third order reactions. Which one is true at a moment for rate of these three reactions if concentration of reactants is same and lesser than $1 \ M$?

For a hypothetical reaction $A + B + C \rightarrow \text{Product}$,the rate is given by $r = -\frac{d[A]}{dt} = K[A]^{1/2}[B]^{1/3}[C]^{1/4}$. The order of the reaction is:

The rate constant of which of the following reactions is independent of the concentration of the reactants?