Problem 37 - Chemistry The Science in Context

Question

One of the compounds in Figure \(\mathrm{P} 10.16\) is insoluble in water; the other has a water solubility of \(0.87 \mathrm{g} / 100 \mathrm{mL}\) at \(20^{\circ} \mathrm{C} .\) Identify which is which, and explain your reasoning.

Step-by-Step Solution

Answer

Question: Identify which compound in Figure P 10.16 is insoluble in water and which has a water solubility of 0.87 g/100 mL at 20°C. Explain your reasoning based on the chemical structures, polarity, and hydrogen bonding. Answer: Without the actual image of Figure P 10.16, it is impossible to provide a definitive answer. However, upon examining the structures in the figure, analyze the polarity and hydrogen bonding capabilities of each compound. The compound with more polar covalent bonds and functionalities that allow for hydrogen bonding is more likely to be soluble in water, and thus have a solubility of 0.87 g/100 mL at 20°C. The other compound, with fewer polar bonds and less potential for hydrogen bonding, will be insoluble in water.

Step 1: Understanding solubility in water

Water is a polar solvent, which means it interacts well with polar compounds (compounds with charged regions) and forms hydrogen bonds. Consequently, polar compounds tend to be soluble in water, whereas nonpolar compounds do not dissolve well in water.

Step 2: Analyzing Compound 1

Analyze the structure of Compound 1 in Figure P 10.16. Determine if it contains polar covalent bonds or functionalities that allow for hydrogen bonding with water.

Step 3: Analyzing Compound 2

Analyze the structure of Compound 2 in Figure P 10.16. Determine if it contains polar covalent bonds or functionalities that allow for hydrogen bonding with water.

Step 4: Comparing solubilities

Compare the structures of compounds 1 and 2, and determine which compound is more likely to be soluble in water based on its polarity and ability to form hydrogen bonds.

Step 5: Identification and reasoning

Identify the insoluble compound and the one with 0.87 g/100 mL solubility in water based on the analysis in steps 2-4. Provide your reasoning for why each compound has the solubility properties described.

Key Concepts

Polar and Nonpolar Compounds

Understanding the difference between polar and nonpolar compounds is essential when it comes to solubility in water. Polar compounds have regions of positive and negative charge due to an unequal distribution of electrons in the molecule. This inequality is often a result of polar covalent bonds where electrons are shared unevenly between atoms of different electronegativities.

Nonpolar compounds, on the other hand, have a more equal distribution of electrons, resulting in no significant charges across the molecule. These differences in charge distribution directly affect a substance's physical properties, including its solubility in water. Water, being a polar molecule itself, dissolves polar compounds effectively because the positive and negative regions can interact with the water molecules through electrostatic attraction.

For nonpolar substances, there is a lack of this attraction, making them insoluble or less soluble in water. Instead, nonpolar compounds often mix well with other nonpolar substances, reflecting the principle 'like dissolves like'.

Hydrogen Bonding

Hydrogen bonding is a special type of dipole-dipole interaction that significantly influences solubility. It occurs when a hydrogen atom is bound to a highly electronegative atom, such as oxygen, nitrogen, or fluorine, forming a polar bond. This hydrogen atom can then interact with a lone pair of electrons on another electronegative atom to form a hydrogen bond.

Hydrogen bonds are particularly important in the context of water solubility. Water molecules, composed of two hydrogen atoms covalently bonded to an oxygen atom, exhibit strong hydrogen bonding capabilities. This ability to form hydrogen bonds is what gives water many of its unique properties, such as its high boiling point and its effectiveness as a solvent for many substances.

Compounds that can form hydrogen bonds with water are generally highly soluble. In the context of the exercise, analyzing compounds to see if they have groups capable of hydrogen bonding with water can help in predicting their solubility.

Polarity of Compounds

Polarity of a compound plays a crucial role in its interaction with solvents, such as water. A molecule's polarity determines its ability to participate in attractive forces like hydrogen bonding or dipole-dipole interactions. Polarity arises from differences in the electronegativity of the atoms within a molecule and the molecule's shape.

A polar molecule has a net dipole moment, with parts of the molecule carrying a partial positive charge and others carrying a partial negative charge, allowing it to interact favorably with other polar molecules or ions. Water's polarity allows it to dissolve ionic compounds, as the partial positive charges on the hydrogen atoms can stabilize negative ions, and the partial negative charge on the oxygen can stabilize positive ions.

In the given exercise, assessing the polarity of the compounds would involve looking at their molecular geometry and bond polarity to determine which one is more likely to be water-soluble. This is an important consideration in the provided step-by-step solution for predicting the solubility of the given compounds.