Q. 74.2( 18 Votes )
State Raoult’s law for a solution containing volatile components. Write two characteristics of the solution which obeys Raoult’s law at all concentrations.
Raoult’s law for volatile solutes states that in a solution, the vapour pressure of a component at a given temperature is equal to the mole fraction of that component in the solution multiplied by the vapour pressure of that component in the pure state.
The vapour pressure P of a solution containing two components A and B is
PA = PoA × XA
PB = P0B × XB
P = PA + PB = PoA × XA + P0B × XB
where, is the vapour pressure of component A
is the vapour pressure of component B
is the vapour pressure of component A in its pure state
is the vapour pressure of component B in its pure state
is the mole fraction of component A
is the mole fraction of component B
Now we know that,
XA + XB = 1
XA = 1- XB
P = (1-XB)P0A + XBP0B
P = P0A + XB(PB0 – P0A)
For a solution to be able to obey Raoult’s law at all concentrations, it should be an ideal solution. For a solution to be called ideal, it should have the following two characteristics:
•The enthalpy of mixing of the pure components to form the solution should be zero, that is, . It means that no heat is absorbed or released during mixing.
•The volume of mixing the pure components should be zero, that is, . This means that the volume of the solution would be equal to the sum of volumes of the two components.
Rate this question :
State Henry’s Law and write its two application?Chemistry - Board Papers
Using Raoult’s law explain how the total vapour pressure over the solution is related to the mole fraction of components in the following solutions.
(i) CHCl3 (l) and CH2Cl2(l)
(ii) NaCl(s) and H2O (l)
Chemistry - Exemplar
Write one stereochemical difference between SN1 and SN2?Chemistry - Board Papers
Note: In the following questions a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices.
Assertion: When NaCl is added to water a depression in freezing point is observed.
Reason: The lowering of the vapour pressure of a solution causes depression in the freezing point.
Chemistry - Exemplar