The colligative nature of the solution
Is the nature of the solution which does not depend on the
type of solute but depends only on the concentration of the solute particle.
The colligative nature of solution consists of two types, there are colligative
nature of the electrolyte solution and the colligative nature of the
nonelectrolyte solution. Although the colligative nature involves the
solution,the colligative nature does not depend on the interaction between
solvent molecules and solutes, but is dependent on the amount of solute being
dissolved in the solution. Colligative properties consist of vapor pressure
depression,boiling point elevation,freezing point depression.
Molality and mole fraction:
In solution,there are
several properties of substances determined solely by the number of solute
particle. Since the colligative nature of the solution is determined by the
number of solute particles,it is necessary to know about the concertration of
solution. Molality is the number of the mole solute in 1 kg of solvent.The
formula of molality is:
m = molality of the
solution
n = mole of the solution
kg = mass of the solvent
mole fraction
The mole fraction is the unit of concentration which
all componentsof the solution are expressed by moles. The mole fraction is the
number of moles equal for mole of all component in the solution. The number of
mole fraction of all component is 1.The formula for mole fraction of solvent is:
xb = mole
fraction of solute
xa = mole
fraction of solvent
Na = mole of
the solvent
Nb = mole of
the solute
Vapor pressure depression
The saturated vapor
pressure of the solution is equal to the solvent mole fraction multiplied by
the vapor pressure of the purified solvent saturated. The formula of vapor
pressure depression in the non electrolyte solution is:
P = saturated vapor
pressure of solution
P0 = saturated
vapor pressure of solvent
Xp = mole
fraction of solvent
Xzt = mole
fraction of solute
Boiling point elevation
Is
a fixed temperature at the time of biling liquid. At this temperature, the
vapor pressure of the liquid is equal to the ambient air pressure. This causes
evaporation throughout the liquid is measured at atmospheric pressure. The
boiling point of the solution is always higher than the boiling point of the
pure solvent. This is due to the presence of solute particle in a solution inhibiting
the evaporation of the solvent particles. Therefore,the evaporation of the solvent
particles requires greater energy. The difference in the boiling point of the
solution with a pure solvent boiling point is called an increase in the boiling
point.
The formula for boiling
point elevation of nonelectrolyte and electrolyte solution is:
Tb
= boiling point elevation
Kb = the
constant increase in molal boiling point
m = molality of the
solution
i = ionizes of the
solution
freezing point depression
the presence of solutes in the solution will cause the
freezing point of the solution to be smaller than the freezing point of the
solvent.
The formula for freezing
point depression of nonelectrolyte and electrolyte solution is :
Tf
= freezing point depression
m = molality of the
solution
i = ionizes of the
solution
Kf = the constant increase
in molal freezing point
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How is the relationship between mole fraction of solute and mole fraction of solvent ?
BalasHapusThe relationship between the mole fraction of the solute and the mole From the solvent is the mole fraction of the solute inversely proportional to the number of moles of solvent and mole of solute
BalasHapusExplain about depression of vapor pressure, boiling point, freezing point of depression. And give an example
BalasHapusVapor pressure depression
HapusThe saturated vapor pressure of the solution is equal to the solvent mole fraction multiplied by the vapor pressure of the purified solvent saturated
Example:
A solvent (such as water) has a vapor pressure denoted by p1. At equilibrium, the gas phase (such as water vapor) above the solvent has a partial pressure equal to p1, but when you add a solute (like table salt, NaCl), the partial pressure of the solvent in the gas phase decreases. The cause is simply that solvent molecules on the surface of the solution have been replaced by solute molecules, which “crowd out” vaporization.
Boiling point elevation
Is a fixed temperature at the time of biling liquid. At this temperature, the vapor pressure of the liquid is equal to the ambient air pressure. This causes evaporation throughout the liquid is measured at atmospheric pressure. The boiling point of the solution is always higher than the boiling point of the pure solvent.
Example:
Because boiling is essentially vaporizing the solvent, boiling point elevation occurs for the same reason as does vapor pressure depression; the solute inhibits vaporization of the solvent at the surface. This presumes the solute is non-volatile, that is, it has a low vapor pressure at room temperature. A volatile solute with a lower boiling point than the solvent may actually depress the boiling point.
freezing point depression
the presence of solutes in the solution will cause the freezing point of the solution to be smaller than the freezing point of the solvent.
Example:
The freezing point of a solution will be lower than that of the pure solvent. A practical application of this colligative property is automotive antifreeze; the freezing point of a 50/50 solution of ethylene glycol (CH2(OH)CH2(OH)) is -33 degrees Celsius (-27.4 degrees Fahrenheit), compared with 0 degrees Celsius (32 degrees Fahrenheit).
In boiling point elevation, what is relationship between ΔTb and Mr of solute?
BalasHapusThe formula of ΔTb :m x kb
Hapusm :n(solute) x mass of solvent(kg)
n(solute) : mass x mr
The relationship between ΔTb and Mr of solute is ΔTb inversely proportional to the Mr of solute that we determined.
Does the electrolyte solution have the same colligative properties as the non-electrolyte solution?
BalasHapusNo, because in electrolyte solution has i(ionezes). (i) can we have from the ionic solution .
HapusExplain the difference between electrolyte solution and strong electrolyte solution?
BalasHapusStrong electrolyte:
BalasHapus1. Completely dissociated at moderate concentrations
2. Conductance increases with dilution but the increase is only slight.
3. There are strong interionic attraction at moderate concentrations.
4. The λm vs √c plot is linear at low concentrations.
Weak Electrolytes:
1. Not completely dissociated at moderate concentrations
2. Conductance increases rapidly with dilution especially near infinite dilution
3. Interionic attractions are not strong even at higher concentrations
4. The λm vs √c plot is not linear even at low concentrations.