Refer to the figure below. Which of the following is TRUE about the polarity of the two compounds? C
A. NH, and BH, are both nonpolar.
B.NH, is nonpolar and BH, is polar.
C. NH, is polar and BH, is nonpolar.
D. NH, and BH, are both polar molecules.
Why does sugar dissolve in water but not in gasoline?
A. Gasoline is a nonpolar molecule.
B. Sugar and water are both polar molecules.
C. Water interacts with the polar areas of sucrose which makes sucrose dissolve in water.
D. All of the above statements explain why sugar dissolves in water but not in gasoline.
What is the polarity of CO, molecules? Why?
A. It is polar, because its charges are distributed symmetrically and its molecular
geometry is symmetrical. B. It is polar, because its charges are distributed asymmetrically and its molecular
geometry is asymmetrical C. It is nonpolar, because its charges are distributed symmetrically and its molecular geometry is symmetrical
D. It is nonpolar, because its charges are distributed asymmetrically and its molecular geometry is asymmetrical
The Correct Answer and Explanation is :
To address each question, let’s start by analyzing each one:
Question 1: Polarity of NH₃ (Ammonia) and BH₃ (Borane)
The question asks about the polarity of NH₃ and BH₃, but you haven’t provided the figure to analyze, so I’ll discuss them based on their molecular structures.
- NH₃ (Ammonia): NH₃ has a trigonal pyramidal shape with nitrogen as the central atom, bonded to three hydrogen atoms. Nitrogen is more electronegative than hydrogen, leading to an uneven distribution of electron density. This results in a net dipole moment, making NH₃ a polar molecule.
- BH₃ (Borane): BH₃, on the other hand, has a trigonal planar structure with boron at the center and three hydrogen atoms surrounding it. Boron is less electronegative than nitrogen, and since the molecule is symmetrical, the dipoles cancel out. This results in no net dipole moment, making BH₃ a nonpolar molecule.
Thus, the correct answer is:
C. NH₃ is polar and BH₃ is nonpolar.
Question 2: Why does sugar dissolve in water but not in gasoline?
Sugar (sucrose) dissolves in water due to the interactions between the polar molecules. Here’s why:
- Sugar and water are both polar molecules: Water is a highly polar solvent due to its bent shape, which creates a dipole. Sucrose is also polar because it contains hydroxyl (OH) groups that form hydrogen bonds with water molecules.
- Water interacts with the polar areas of sucrose: The hydroxyl groups in sugar form hydrogen bonds with water molecules, allowing sugar to dissolve in water. In contrast, gasoline is nonpolar and does not interact well with polar molecules like sugar.
So, the correct answer is:
D. All of the above statements explain why sugar dissolves in water but not in gasoline.
Question 3: Polarity of CO₂ (Carbon Dioxide) molecules
CO₂ has a linear molecular geometry with carbon in the center and two oxygen atoms on either side. Both C=O bonds are polar due to the difference in electronegativity between carbon and oxygen, but the molecule itself is symmetrical. The symmetry causes the dipoles to cancel each other out.
Thus, the correct answer is:
C. It is nonpolar, because its charges are distributed symmetrically and its molecular geometry is symmetrical.
Summary Explanation
- Ammonia (NH₃) is polar because of its trigonal pyramidal shape and the electronegativity difference between nitrogen and hydrogen, creating an overall dipole moment.
- Borane (BH₃) is nonpolar due to its symmetrical trigonal planar geometry, where the dipoles cancel each other.
- Sugar dissolves in water because both are polar and can form hydrogen bonds with each other. Gasoline, being nonpolar, cannot interact effectively with sugar.
- CO₂ is nonpolar because its linear structure results in the cancellation of the dipoles despite the polar bonds between carbon and oxygen.
I hope this clears up the concepts! Let me know if you need further clarification.