What is the expected van’t Hoff factor for CO2, KBr, CaCl2, CH3CH2OH, and FeCl3?
The correct answer and explanation is:
The van’t Hoff factor (i) represents the number of particles into which a substance dissociates in solution. It is important for understanding colligative properties like boiling point elevation, freezing point depression, and osmotic pressure. For ionic compounds, the van’t Hoff factor corresponds to the number of ions produced in solution, while for molecular compounds, it is usually 1, since they do not dissociate into ions.
Here is the expected van’t Hoff factor for the given substances:
- CO2 (Carbon Dioxide): The van’t Hoff factor for CO2 is 1. Carbon dioxide is a molecular compound and does not dissociate into ions when it dissolves in water. Therefore, it exists as individual CO2 molecules in solution.
- KBr (Potassium Bromide): The van’t Hoff factor for KBr is 2. Potassium bromide is an ionic compound, and when it dissolves in water, it dissociates completely into two ions: K+ and Br−. Therefore, the van’t Hoff factor is 2.
- CaCl2 (Calcium Chloride): The van’t Hoff factor for CaCl2 is 3. Calcium chloride is an ionic compound, and when it dissolves, it dissociates into three ions: Ca2+ and two Cl− ions. Hence, the van’t Hoff factor is 3.
- CH3CH2OH (Ethanol): The van’t Hoff factor for ethanol is 1. Ethanol is a molecular compound and does not dissociate into ions in solution. Therefore, it stays as individual ethanol molecules in solution.
- FeCl3 (Iron(III) Chloride): The van’t Hoff factor for FeCl3 is 4. Iron(III) chloride is an ionic compound that dissociates into four ions in solution: Fe3+ and three Cl− ions. As a result, the van’t Hoff factor for FeCl3 is 4.
In summary, the van’t Hoff factor reflects the number of particles produced by the dissociation of a substance in solution. For molecular compounds, the factor is typically 1, while for ionic compounds, it corresponds to the number of ions produced during dissociation.