Which of the following is most likely to be a gas at room temperature? A) K₂S B) C₈H₁₈ C) MgF₂ D) F₂ E) H₂O

Question

I am fairly certain its F2, but an explanation would be appreciated!!!

Answer 1

F2

Say something about intermolecular force strength.

Weakest IMF's = most likely to be vaporized.

Relative strength of IMF's

(strongest)NIMHDL(weakest)

N=network covalent

I=ionic

M=metallic

H=hydrogen bonds (H bonded to FON, FON has lone pair)

D=dipole dipole (molecule is polar)

L=London dispersion (nonpolar molecules, all molecules)

K2S=ionic

C8H18=nonpolar, london dispersion

MgF2=ionic

F2=nonpolar, london dispersion

H2O=polar(dipole-dipole), and hydrogen bonds

So, C8H18 and F2 have the weakest IMF type (london dispersion).

Dispersion forces are stronger when the molecule has a bigger electron cloud, because the temporary dipoles it makes are more polar. The nonpolar thing becomes polar momentary with dispersion forces, and the more polar it becomes, the stronger the force.

C8H18 has a bigger mass/electron cloud, so it has stronger dispersion forces than F2.

This means that F2 has the weakest imf's, and is easiest to vaporize, and is most likely to be a gas.