Which one of the following exhibits dipole-dipole attraction between molecules?
Question 18 options:
a) AsH3
b) Br2
c) PI3
d) BCl3
e) NO2
The correct answer is c) PI3. PI3 exhibits dipole-dipole attraction between molecules because it is a polar molecule with a positive and a negative end. The other options (a) AsH3, (b) Br2, (d) BCl3, and (e) NO2 do not exhibit dipole-dipole attraction between molecules.
The compound that exhibits dipole-dipole attraction between molecules is option a) AsH3 (arsine).
To determine which one of the given options exhibits dipole-dipole attraction between molecules, we need to examine the molecular structure of each compound. Dipole-dipole attractions occur when a compound has polar bonds and an uneven distribution of charge, resulting in the positive region of one molecule being attracted to the negative region of another molecule.
Let's analyze each option:
a) AsH3 (arsine): Arsenic trihydride has a trigonal pyramidal molecular shape, with the central arsenic atom bonded to three hydrogen atoms. Each As-H bond is polar due to the difference in electronegativity between arsenic (2.18) and hydrogen (2.20). Therefore, dipole-dipole attractions can exist between AsH3 molecules.
b) Br2 (diatomic bromine): Bromine is a diatomic molecule composed of two bromine atoms. Since both atoms have the same electronegativity (2.96), there is no difference in electronegativity, and thus, no dipole-dipole attractions between Br2 molecules.
c) PI3 (phosphorus triiodide): Phosphorus triiodide has a pyramidal molecular shape, with the central phosphorus atom bonded to three iodine atoms. Each P-I bond is polar, but the overall molecule is nonpolar due to the symmetric arrangement of the three iodine atoms. Therefore, dipole-dipole attractions cannot exist between PI3 molecules.
d) BCl3 (boron trichloride): Boron trichloride has a trigonal planar molecular shape, with the central boron atom bonded to three chlorine atoms. While the B-Cl bonds are polar, the overall molecule is nonpolar due to the symmetric arrangement of the chlorine atoms. Therefore, dipole-dipole attractions cannot exist between BCl3 molecules.
e) NO2 (nitrogen dioxide): Nitrogen dioxide has a bent molecular shape, with the central nitrogen atom bonded to two oxygen atoms. The N-O bond is polar due to the difference in electronegativity between nitrogen (3.04) and oxygen (3.44). Therefore, dipole-dipole attractions can exist between NO2 molecules.
Based on this analysis, the compound that exhibits dipole-dipole attraction between molecules is option A) AsH3.