Question

rank the elements or compounds in the table below in decreasing order of their boiling points. that is, choose 1 next to the substance with the highest boiling point, choose 2 next to the substance with the next - highest boiling point, and so on.
substance chemical symbol, chemical formula or lewis structure
a cr
b ar
c h - c - c - c - c - h

h h h h
|
o
d h - c - n - c - h

h h h h
| |
o h

Explanation:

Step1: Analyze intermolecular forces

Substance D has hydrogen - bonding (due to N - H and O - H bonds), which is a strong intermolecular force. Substance C has dipole - dipole forces (polar C - O bond) and London dispersion forces. Argon (Ar) and Chromium (Cr) are noble gas and metal respectively. Argon has only London dispersion forces and chromium has metallic bonding.

Step2: Rank boiling points

Hydrogen - bonding in D leads to the highest boiling point among these. Then comes C with dipole - dipole and London dispersion forces. Argon has relatively low boiling point due to weak London dispersion forces and chromium has a high boiling point due to metallic bonding but generally for these substances in comparison, the order from highest to lowest boiling point is D > C > Cr > Ar.

Answer:

D, C, Cr, Ar