While secondary akyl halides react both by SN1 and SN2 mechanism depending on the conditions of the reaction, they react faster under SN2 conditions if the alkyl halide substrate is not hindered by bulky groups. This is because the nucleophile accesses the carbon atom more easily from the backside making SN2 mechanism faster than SN1
The stability of the carbocation can the type SN1 be favored and by decreasing the steric hindrance can the type of reaction SN2 be favored.
Explanation:
The type of SN reaction works through the formation of the carbocation and its rate depends on the stability. The type of SN2 reaction leads to the formation of the transition and its rate is dependent for the secondary alkyl halide. for a secondary alkyl halide, both type SN1 and type SN2 favor this reaction in the same way, but only by increasing the stability of the carbocation can the type SN1 be favored and by decreasing the steric hindrance can the type of reaction SN2 be favored.
The formula or chemical formula of a compound is same irrespective of source / mode of synthesis . Thus if a sample of compound has one carbon atom for every two atoms of oxygen (CO2), the formula will remains the same
So the answer is that for all other samples the compound X should hold this ration true.