A 1 m solution of MgCl2 will cause the decrease in the freezing point of water to be approximately ___ than that caused by a 1 m solution of sucrose
a. 3x kleiner/ 3x smaller
b. 2x kleiner / 2x smaller
c. dieselfde / the same
d. 2x groter / 2x greater
e. 3x groter / 3x greater
f. nie een van bogenoemde nie / none of the above
Sucrose does not ionize. MgCl2 ionizes into three particles. Since the depression of the freezing point is proportional to the number of particles, th MgCl2 will depress 3x greater.
3 times greater
To determine the change in the freezing point of water caused by a 1 m solution of MgCl2 compared to a 1 m solution of sucrose, we need to consider the concept of freezing point depression.
Freezing point depression occurs when a non-volatile solute, such as MgCl2 or sucrose, is added to a solvent, in this case, water. The presence of the solute lowers the freezing point of the solvent.
The freezing point depression equation is given by:
ΔTf = Kf * m * i
Where:
ΔTf is the change in freezing point,
Kf is the cryoscopic constant specific to the solvent (water),
m is the molality (moles of solute per kilogram of solvent),
i is the van't Hoff factor, which represents the number of particles that the solute dissociates into in the solution.
To compare the change in freezing point caused by the two solutions, we need to consider the molality and van't Hoff factor for each solute.
For a 1 m solution of MgCl2:
- The molality (m) is 1 m (since it is a 1 m solution).
- The van't Hoff factor (i) for MgCl2 is 3, because it dissociates into three particles in solution; one Mg2+ ion and two Cl- ions.
For a 1 m solution of sucrose:
- The molality (m) is 1 m (since it is a 1 m solution).
- The van't Hoff factor (i) for sucrose is 1, because it does not dissociate into ions in solution.
Now, let's compare the two solutions:
The change in freezing point (ΔTf) for the MgCl2 solution can be calculated as ΔTf = Kf * m * i = 3 * Kf * 1 * 3 = 9 * Kf.
The change in freezing point (ΔTf) for the sucrose solution can be calculated as ΔTf = Kf * m * i = 1 * Kf * 1 * 1 = Kf.
Since the change in freezing point caused by the MgCl2 solution (9 * Kf) is larger than that caused by the sucrose solution (Kf), we can conclude that the decrease in the freezing point of water caused by a 1 m solution of MgCl2 is approximately 9 times greater than that caused by a 1 m solution of sucrose.
Therefore, the correct answer is:
e. 3x groter / 3x greater