Which of the following molecules contains two nitrogen atoms and is highly soluble in water?

• A. Nitrous oxide (N2O)
• B. Nitrogen gas (N2)
• C. Ammonia (NH3)
• D. Urea (NH2CONH2)

Answer: (D)

Verified step by step guidance

1. Identify the molecular formulas of each compound listed: Nitrous oxide (N2O), Nitrogen gas (N2), Ammonia (NH3), and Urea (NH2CONH2).
2. Count the number of nitrogen atoms in each molecule by examining their formulas. For example, N2O has 2 nitrogen atoms, N2 has 2 nitrogen atoms, NH3 has 1 nitrogen atom, and NH2CONH2 has 2 nitrogen atoms.
3. Consider the polarity and hydrogen bonding capability of each molecule, since solubility in water depends largely on these factors. Water is a polar solvent and dissolves polar molecules or those capable of hydrogen bonding well.
4. Analyze the structure of urea (NH2CONH2), noting that it contains two amine groups (NH2) and a carbonyl group (C=O), which can form multiple hydrogen bonds with water molecules, increasing its solubility.
5. Compare this to the other molecules: Nitrous oxide and nitrogen gas are nonpolar or weakly polar and do not form hydrogen bonds effectively, while ammonia has only one nitrogen and fewer hydrogen bonding sites, making urea the molecule with two nitrogen atoms and the highest water solubility.