Consider the following 2 molecules: arsane which has the molecular formula AsH3, and dimethylether, an ether which has the molecular formula C2H6O. Which of these molecules is polar? a. Dimethylether is polar but arsane is not. b. Both are polar. c. Neither are polar. d. Arsane is polar but dimethylether is not.  Consider a pure sample of silane which has the formula SiH4. Of the options listed below, what is the strongest attractive force in this sample? a. Ionic bonding b. Ion-dipole forces c. Hydrogen bonding d. Dispersion forces e. Dipole-dipole forces
1) Consider the following 2 molecules: arsane which has the molecular formula AsH3, and dimethylether, an ether which has the molecular formula C2H6O.
Which of these molecules is polar?
a. Dimethylether is polar but arsane is not. b. Both are polar. c. Neither are polar. d. Arsane is polar but dimethylether is not. ÂÂ
Consider a pure sample of silane which has the formula SiH4. Of the options listed below, what is the strongest attractive force in this sample?
a. Ionic bonding
b. Ion-dipole forces c. Hydrogen bonding d. Dispersion forces e. Dipole-dipole forces
The Correct Answer and Explanation is :
Answer:
1) Correct answer: (b) Both are polar.
2) Correct answer: (d) Dispersion forces.
Explanation:
1. Polarity of Arsane (AsH₃) and Dimethyl Ether (C₂H₆O)
To determine the polarity of a molecule, we need to evaluate its molecular geometry and electronegativity differences.
- Arsane (AsH₃):
Arsane (AsH₃) is structurally similar to ammonia (NH₃). Arsenic (As) belongs to Group 15 and has a lone pair of electrons, resulting in a trigonal pyramidal molecular geometry. Because arsenic is more electronegative than hydrogen (but not significantly), and the molecule has an asymmetrical shape due to the lone pair, AsH₃ is polar. - Dimethyl Ether (C₂H₆O):
Dimethyl ether has the structure CH₃-O-CH₃, where the oxygen is bonded to two carbon atoms. The oxygen atom has two lone pairs, which create a bent geometry (similar to water). Oxygen is much more electronegative than carbon and hydrogen, leading to an uneven charge distribution. Since the molecule is asymmetrical, dimethyl ether is polar.
Thus, both molecules are polar, making option (b) the correct choice.
2. Strongest Intermolecular Force in Silane (SiH₄)
To determine the strongest force in SiH₄, let’s analyze the possible intermolecular forces:
- Ionic bonding: Silane is a covalent molecule, not an ionic compound, so this does not apply.
- Ion-dipole forces: These occur between ions and polar molecules, which is not relevant to SiH₄.
- Hydrogen bonding: Hydrogen bonding occurs when hydrogen is bonded to highly electronegative atoms (N, O, F), which does not happen in SiH₄.
- Dipole-dipole forces: SiH₄ has a tetrahedral geometry, and silicon and hydrogen have very small electronegativity differences, making it a nonpolar molecule, meaning dipole-dipole forces do not apply.
- Dispersion forces: Since SiH₄ is nonpolar, the only intermolecular force present is London dispersion forces, which arise from temporary dipoles.
Since dispersion forces are the only forces acting in pure SiH₄, the correct answer is (d) Dispersion forces.