Grade 12 chemistry
Which one of the following exhibits dipole-dipole attraction between molecules?
Question 18 options:
a) AsH3
b) Br2
c) PI3
d) BCl3
e) NO2
is the answer a)?
No, the correct answer is e) NO2.
To determine which one of the options exhibits dipole-dipole attraction between molecules, we need to determine if the molecule has a polar bond and if the overall molecular shape allows for dipole-dipole interactions.
In a polar bond, there is an unequal sharing of electrons between two atoms due to differences in electronegativity. This results in one atom having a partial positive charge (δ+) and the other having a partial negative charge (δ-).
The molecular shape also plays a role in determining whether dipole-dipole interactions can occur. For dipole-dipole interactions to take place, the molecule must have a permanent dipole (a separation of positive and negative charges) that does not cancel out with other dipoles in the molecule.
Now let's examine each option:
a) AsH3 (Arsine) - This molecule has a polar bond (As-H) due to the difference in electronegativity between the atoms. It also has a pyramidal shape, which allows for a permanent dipole moment. Therefore, it exhibits dipole-dipole attraction between molecules.
b) Br2 (Bromine) - Bromine is a diatomic element, so it does not have multiple atoms and cannot have dipole-dipole attractions. Therefore, it does not exhibit dipole-dipole attraction between molecules.
c) PI3 (Phosphorus triiodide) - This molecule has polar bonds (P-I) due to the difference in electronegativity between the atoms. However, it has a pyramidal shape, which allows for a permanent dipole moment. Therefore, it exhibits dipole-dipole attraction between molecules.
d) BCl3 (Boron trichloride) - Boron trichloride has three polar bonds (B-Cl) due to the difference in electronegativity between the atoms. However, it has a trigonal planar shape, which results in the cancellation of dipole moments. Therefore, it does not exhibit dipole-dipole attraction between molecules.
e) NO2 (Nitrogen dioxide) - This molecule has polar bonds (N-O) due to the difference in electronegativity between the atoms. It also has a bent shape, which allows for a permanent dipole moment. Therefore, it exhibits dipole-dipole attraction between molecules.
Based on the analysis, both AsH3 and PI3 exhibit dipole-dipole attraction between molecules. So, the correct answer could be either a) AsH3 or c) PI3.
The correct answer is e) NO2.
Dipole-dipole attractions occur when polar molecules have permanent dipole moments and interact with each other. Among the options, NO2 is the only molecule with a permanent dipole moment due to the difference in electronegativity between nitrogen (N) and oxygen (O). AsH3, Br2, PI3, and BCl3 do not have permanent dipole moments, so they do not exhibit dipole-dipole attractions.