Solubility and Intermolecular Forces: Practice Questions and Guidance

Q1. Give the major force between acetone and chloroform.

Background

Topic: Intermolecular Forces

This question tests your understanding of the types of intermolecular forces that can exist between molecules, specifically between acetone and chloroform.

Key Terms and Concepts:

• Dispersion forces: Present in all molecules, especially nonpolar ones.

• Hydrogen bonding: Occurs when H is bonded to N, O, or F and interacts with another electronegative atom.

• Ion-ion: Forces between charged ions.

• Dipole-dipole: Forces between polar molecules.

• Ion-dipole: Forces between an ion and a polar molecule.

Step-by-Step Guidance

1. Identify the molecular structure and polarity of acetone and chloroform. Acetone is a polar molecule (contains a C=O group), and chloroform is also polar (contains a C-H bond and three Cl atoms).

2. Consider the types of intermolecular forces possible between two polar molecules. Both dipole-dipole and hydrogen bonding may be possible, but hydrogen bonding requires specific atoms.

3. Check if either molecule can act as a hydrogen bond donor or acceptor. Chloroform has a hydrogen attached to a highly electronegative atom (Cl), and acetone has an oxygen atom.

4. Review the options and eliminate those that do not apply (e.g., ion-ion, ion-dipole).

Try solving on your own before revealing the answer!

Final Answer: Hydrogen bonding

The major force between acetone and chloroform is hydrogen bonding, because chloroform can donate a hydrogen (attached to Cl) and acetone can accept it via its oxygen atom.

Q2. Which of the following compounds will be most soluble in water (H2O)?

Background

Topic: Solubility and "Like Dissolves Like" Principle

This question tests your ability to predict solubility based on molecular structure and polarity.

Key Terms and Concepts:

• Polar molecules: Molecules with uneven charge distribution, often soluble in water.

• Nonpolar molecules: Molecules with even charge distribution, generally insoluble in water.

• Hydrogen bonding: Increases solubility in water if the molecule can form hydrogen bonds.

Step-by-Step Guidance

1. Examine the structure of each compound listed: carbon tetrachloride (CCl4), pentane, butane, and ethylene glycol.

2. Determine which compounds are polar and which are nonpolar. Water is polar, so polar compounds are more likely to dissolve.

3. Look for functional groups that can hydrogen bond with water (e.g., -OH groups).

4. Compare the number and type of polar groups in each compound to predict which will be most soluble.

Try solving on your own before revealing the answer!

Final Answer: Ethylene glycol (HOCH2CH2OH)

Ethylene glycol is most soluble in water because it is highly polar and can form multiple hydrogen bonds with water molecules.