Question

Which alkyl halide has the highest density and why?

Answer 1

Hint: Density of any substance is the mass of that substance distributed per volume. Alkyl halides are formed by the introduction of a halogen into the hydrocarbon alkane. As the mass of any substance increases its density also increases, but increase in volume of any compound decreases the density.

Complete answer:
Density of any substance is defined as its mass in per unit volume of that substance. So, density has a formula, denoted by rho, $\rho =\dfrac{mass}{volume}$ . Therefore, by increasing the mass of any compound the density increases and by increasing the volume of that compound the density decreases.
We have been given to find which alkyl halide has the highest density and its reason. Alkyl halides are compounds formed when a halogen like F, Cl, Br, I is introduced into the hydrocarbon chain.
For any hydrocarbon, as the number of carbons in the chain or the alkyl group’s increases, they increase the surface area thereby increasing the volume of the compound, so it decreases the density. So the alkyl group with more density will be methyl $C{{H}_{3}}$. While, the size of the halide affects the density as the size and mass of the halide having greater atomic number will be the most, so iodine that is the last heaviest halide will have more mass, therefore alkyl having methyl and iodine that is methyl iodide will have the highest density.
Hence, methyl iodide $C{{H}_{3}}I$ has the highest density due to the less volume of alkyl and the heavier iodine.

Note:
The increase in surface area of the hydrocarbon affects the boiling point also, as the surface area increases, the van der Waal forces increase that increases the boiling point. The volume also increases as less number of particles are occupied in a larger volume, but in methyl the more atoms are occupied in lesser area.