Water freezing point depression constant

A = Kj- Cflj A 7b = Ki) Cflj We use molality in these equations because they describe temperature changes. The constant Zf is called the freezing point depression constant, and is called the boiling point elevation constant. These constants are different for different solvents but do not depend on the identity of the solutes. For water, Zf is 1.858 °C kg/mol and is 0.512 °C kg/mol. 

The freezing point depression constant for water is known from experiments and can be found in tables Tf = 1.858 ° C kg/mol. To calculate the freezing point, we must first determine the molality of the... 

The solution in question 3 freezes at -0.192°C. Because water normally freezes at 0°C, this means that the freezing point has decreased by 0.192°C. Thus, ATf = -0.192°C. What is the freezing point depression constant of water, Kfl... 

The depression of the freezing point of a solvent due to the presence of a dissolved solute is an example of a colligative property, that is, a property of a dilute solution that depends on the number of dissolved particles and not on the identity of the particles. Water has a freezing point depression constant, Kf, of 1.86 K kg mol-1. In other words, for every mole of nonvolatile solute dissolved in a kilogram of water, the freezing point of water is lowered by 1.86°C. The change in freezing point, A T, can be calculated from the equation... 

IQ = molal freezing-point depression constant Kb = molal boiling-point elevation constant Kf for water = 1.86 K kg mol-1 for water = 0.512 K kg mol-1 AT = iKf x molality ATb = iKb x molality n = MRT... 

B) This problem can be solved using the factor-label method. The freezing point depression constant (kd for water is 1.86°C m ... 

A solution also exhibits a depression in its freezing point. The freezing point depression is the decrease in the temperature of the freezing point due to the addition of a solute. It is calculated using the equations ATj. = Kjm, where ATj. is the decrease in freezing point for the solution, Kj. is the molal freezing point depression constant, and m is the molality of the solution. Water s K. value is 1.86°C/m. 

PROBLEM 11.20 Assuming complete dissociation, what is the molality of an aqueous solution of KBr whose freezing point is —2.95°C The molal freezing-point-depression constant of water is given in Table 11.4. 

Certain properties of solutions depend only on the number of solute particles dissolved in a given amount of solvent and not on the nature of these particles. Such properties are called colligative properties. For example, one such property is the freezing point depression. One mole of any solute dissolved in 1000 g of water lowers the freezing point of the water by 1.86°C. We call this value, 1.86 degree/mole/1000 g water, the freezing point depression constant of water, Kf. Each solvent has a characteristic freezing point depression constant that is related to its heat of fusion. The nature of the solute does not matter. 

You used 0.5 M glucose and 3% NaCl aqueous solutions in your tonicity experiments. What would be the freezing points of each of these solutions, considering that the freezing point depression constant of water is 1.86°C/osmol ... 

Glycol (C2H602) is the main component in antifreeze. What mass of glycol must be added to 10 liters of water to prevent freezing down to -18.6°C (The molal freezing point depression constant for water is 1.86°C kg/mol.)... 

The freezing point depression constant for cyclohexane is 20.3, which is very high when compared to the 1.86 for water. You need 20-30 mL of pure material in order to make several measurements, and all you have available is some technical-grade material that was prepared by catalytic hydrogenation. You are to do an extractive distillation to remove the benzene impurity. 

In principle, any of the colligative properties can be used to find the solute s molar mass, but in practice, some systems provide more precise data than others. For example, to determine the molar mass of an unknown solute by freezing point depression, you would select a solvent with as large a molal freezing point depression constant as possible (see Table 13.5). If the solute is soluble in acetic acid, for instance, aim concentration of it depresses the freezing point of acetic acid by 3.90°C, more than twice the change in water (1.86°C). 

Challenge A 0.045m solution (consisting of a nonvolatile, nonelectrolyte solute) is experimentally found to have a freezing point depression of 0.08°C. What is the freezing point depression constant (/Cf). Which is most likely to be the solvent water, ethanol, or chloroform ... 

Ans. The freezing point depression constant for water is 1.86 °C/molal. Because the solute was a nonionizing solid, the factor i = 1. Using those factors in the equation for freezing point depression, = -iKfm ... 

The values of Kp the molal freezing-point-depression constant, for several common solvents are given in Table 13.3. For water, Kfvs 1.86 °C/m.Therefore, any aqueous solution that is 1 w in nonvolatile solute particles (such as 1 tn C6H12O6 or 0.5 m NaCl) freezes at the temperature that is 1.86 °C lower than the freezing point of pure water. 

ATt is the amount the freezing point will be lowered, K, is the freezing point depression constant (1.86°C k mol for water), and m is the molality of the particles. 

The proportionality constants, Kf and K, are, respectively, the molal freezing-point depression constant and the molal boiling-point elevation constant The freezing-and boiling-point constants are properties of the solvent, no matter what the solute may be. The freezing-point constant for water is 1.86°C/m, and the boiling-point constant is 0.52°C/m. 

The molar enthalpy change of fusion of water is equal to 6.01 kJ mol Show that the value of the freezing point depression constant for water is equal to 1.86Kkgmol. ... 

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