How many of the following molecules are polar? XeO2, SiCl2Br2, C2Br2, SeCl6. a) 1 b) 2 c) 3 d) 4 e) 5
The Correct Answer and Explanation is:
Let’s evaluate the polarity of each molecule one by one by considering their molecular geometry and the distribution of charge.
- XeO2 (Xenon dioxide):
- Xenon is in group 18, so it has a full valence shell. In XeO2, the xenon atom is double-bonded to two oxygen atoms, forming a linear molecular geometry.
- The oxygen atoms are electronegative, causing a dipole moment. However, since the molecule is linear, the dipoles cancel each other out. Therefore, XeO2 is nonpolar.
- SiCl2Br2 (Silicon dichloride dibromide):
- Silicon in this molecule is bonded to two chlorine atoms and two bromine atoms in a tetrahedral geometry. The chlorine and bromine atoms have different electronegativities, so the dipoles do not cancel out.
- The unequal distribution of charge results in a polar molecule.
- C2Br2 (Dibromoethene):
- In this molecule, each carbon is bonded to one hydrogen and one bromine, forming a linear structure. Due to the presence of two different halogens (bromine and hydrogen), there will be a dipole moment.
- As the molecule is not symmetric, the dipoles do not cancel out. Therefore, C2Br2 is polar.
- SeCl6 (Selenium hexachloride):
- Selenium in SeCl6 is surrounded by six chlorine atoms in an octahedral geometry. The chlorine atoms are arranged symmetrically around the central selenium atom, which means the individual dipole moments cancel out.
- Therefore, SeCl6 is nonpolar.
Conclusion:
- XeO2 is nonpolar.
- SiCl2Br2 is polar.
- C2Br2 is polar.
- SeCl6 is nonpolar.
Thus, 2 of the molecules are polar. The correct answer is b) 2.
