The major product of the following reaction is:

Aqueous solutions of Na$$_2$$S$$_2$$O$$_3$$ on reaction with Cl$$_2$$ gives:

Native silver metal forms a water soluble complex with a dilute aqueous solution of NaCN in the presence of:

Under the same reaction conditions, initial concentration of 1.386 mol dm$$^{-3}$$ of a substance becomes half in 40 seconds and 20 seconds through first order and zero order kinetics, respectively. Ratio $$\left( {{{{k_1}} \over {{k_0}}}} \right)$$ of the rate constants for first order ($$k_1$$) and zero order ($$k_0$$) of the reactions is: