Nitrogen, $$$N_{2}$$$, and carbon monoxide, $$$C O$$$, both have $$$M_{\mathrm{r}}=28$$$. The boiling point of $$$\mathrm{N}_{2}$$$ is $$$77 \mathrm{~K}$$$. The boiling point of $$$\mathrm{CO}$$$ is $$$82 \mathrm{~K}$$$. What could be responsible for this difference in boiling points?

CO molecules have a permanent dipole, the $\mathrm{N}_{2}$ molecules are not polar.

$\mathrm{N}_{2}$ has $\sigma$ and $\pi$ bonding, $\mathrm{CO}$ has $\sigma$ bonding only.

$\mathrm{N}_{2}$ has a strong $\mathrm{N} \equiv \mathrm{N}$ bond, $\mathrm{CO}$ has a $\mathrm{C}=\mathrm{O}$ bond.

The $\mathrm{CO}$ molecule has more electrons than the $\mathrm{N}_{2}$ molecule.

Chemistry

IGCSE&ALevel

CAIE

Exam No：9701_w15_qp_13 Year：2015 Question No：4

Answer:

Knowledge points:

3.6.1.1 describe hydrogen bonding, limited to molecules containing N–H and O–H groups, including ammonia and water as simple examples

3.6.1.2.1 its relatively high melting and boiling points

3.6.1.2.2 its relatively high surface tension

3.6.1.2.3 the density of the solid ice compared with the liquid water

3.6.2 use the concept of electronegativity to explain bond polarity and dipole moments of molecules

3.6.3.1 describe van der Waals’ forces as the intermolecular forces between molecular entities other than those due to bond formation, and use the term van der Waals’ forces as a generic term to describe all intermolecular forces

3.6.3.2.1 instantaneous dipole – induced dipole (id-id) force, also called London dispersion forces

3.6.3.2.2 permanent dipole – permanent dipole (pd-pd) force, including hydrogen bonding

3.6.3.2.3 tdescribe hydrogen bonding and understand that hydrogen bonding is a special case of permanent dipole – permanent dipole force between molecules where hydrogen is bonded to a highly electronegative atom

3.6.3.3 describe hydrogen bonding and understand that hydrogen bonding is a special case of permanent dipole – permanent dipole force between molecules where hydrogen is bonded to a highly electronegative atom

3.6.4 stae that, in general, ionic, covalent and metallic bonding are stronger than intermolecular forces

Nitrogen, $$\(N_{2}\)$$, and carbon monoxide, $$\(C O\)$$, both have $$\(M_{\mathrm{r}}=28\)$$. The boiling point of $$\(\mathrm{N}_{2}\)$$ is $$\(77 \mathrm{~K}\)$$. The boiling point of $$\(\mathrm{CO}\)$$ is $$\(82 \mathrm{~K}\)$$. What could be responsible for this difference in boiling points?

Answer:

Knowledge points:

Solution:

Nitrogen, $$\(N_{2}\)$$, and carbon monoxide, $$\(C O\)$$, both have $$\(M_{\mathrm{r}}=28\)$$. The boiling point of $$\(\mathrm{N}_{2}\)$$ is $$\(77 \mathrm{~K}\)$$. The boiling point of $$\(\mathrm{CO}\)$$ is $$\(82 \mathrm{~K}\)$$. What could be responsible for this difference in boiling points?

Answer:

Knowledge points:

Solution:

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