Which has the lowest freezing point?Select one of the options below as your answer: A. pure water B. 0.5 M ionic NaCl C. 0.5 M ionic CaCl2 D. 0.5 M ionic AlCl3 E. 0.5 M molecular C12H22O11
There are two ways to solve this.
1. Use delta T = i*Kf*m and calculate each of the five choices, then pick the winner.
2. Reason.
If delta T = i*Kf*m and you realize that Kf and M are the same for everything, then just look at i. m is molality and your capital M means molarity; I don't know if that's a typo but the difference is too small to worry about for this problem.
i for NaCl = 2
i for CaCl2 = 3
i for AlCl3 = 4
i for C12H22O11 = 1
To determine which solution has the lowest freezing point, we need to consider the concept of freezing point depression, which is the phenomenon where the presence of solutes in a solvent lowers its freezing point.
The degree of freezing point depression depends on the concentration and nature of the solute particles. Ionic compounds dissociate into ions in water, which leads to the formation of more particles and a greater freezing point depression than molecular compounds.
Here are the options:
A. Pure water is a molecular compound and does not dissociate into ions. Therefore, it will have the highest freezing point among the given options.
B. 0.5 M ionic NaCl: When NaCl is dissolved in water, it dissociates into Na+ and Cl- ions. The presence of these ions will result in freezing point depression, but NaCl has only two ions in solution, so the freezing point depression will be less compared to the compounds with more ions.
C. 0.5 M ionic CaCl2: Similarly, when CaCl2 is dissolved in water, it dissociates into Ca2+ and 2Cl- ions. Presence of three ions will cause a greater freezing point depression than NaCl.
D. 0.5 M ionic AlCl3: AlCl3 dissociates into Al3+ and 3Cl- ions when dissolved in water. The presence of four ions means that the freezing point depression will be greater than that of CaCl2.
E. 0.5 M molecular C12H22O11: This solution contains a molecular compound, meaning it does not dissociate into ions like the ionic compounds. Hence, its freezing point depression will be lower than that of the ionic compounds.
Considering these explanations, the option with the lowest freezing point will be E. 0.5 M molecular C12H22O11.