CBSE 2025 · Region 4 · Set 1 · Q29 · 4 marks
According to the generally accepted definition of the ideal solution there are equal interaction forces acting between molecules belonging to the same or different species. (This is equivalent to the statement that the activity of the components equals the concentration.) Strictly speaking, this condition is fulfilled only in exceptional cases for mixtures (optical isomers, isotopic mixtures of an element, hydrocarbon mixtures). It is still usual to talk about ideal solutions as limiting cases in reality since very dilute solutions behave ideally with respect to the solvent. This view is further supported by the fact that Raoult's law empirically found for describing the behaviour of the solvent in dilute solutions can be deduced thermodynamically via the assumption of ideal behaviour of the solvent. Answer the following questions :(a)Give one example of miscible liquid pair which shows negative deviation from Raoult's law. What is the reason for such deviation ?(b)State Raoult's law for a solution containing volatile components.(ii)Raoult's law is a special case of Henry's law. Comment.(c)Write two characteristics of an ideal solution.
According to the generally accepted definition of the ideal solution there are equal interaction forces acting between molecules belonging to the same or different species. (This is equivalent to the statement that the activity of the components equals the concentration.) Strictly speaking, this condition is fulfilled only in exceptional cases for mixtures (optical isomers, isotopic mixtures of an element, hydrocarbon mixtures). It is still usual to talk about ideal solutions as limiting cases in reality since very dilute solutions behave ideally with respect to the solvent. This view is further supported by the fact that Raoult's law empirically found for describing the behaviour of the solvent in dilute solutions can be deduced thermodynamically via the assumption of ideal behaviour of the solvent. Answer the following questions :
(a)
Give one example of miscible liquid pair which shows negative deviation from Raoult's law. What is the reason for such deviation ?
(b)
State Raoult's law for a solution containing volatile components.
(ii)
Raoult's law is a special case of Henry's law. Comment.
(c)
Write two characteristics of an ideal solution.
Marking-scheme solution
(a)
Chloroform and Acetone
A-B interactions are stronger than A-A and B-B interaction.
(i)
For any solution the partial vapour pressure of each volatile component is directly
proportional to its mole fraction.
(b)
(ii)
;
When p0 = KH
p α ꭓ for both.
(c)
The enthalpy of mixing of the pure components in the ideal solution is Zero/∆mixH=0.
The Volume of mixing of the pure components in the ideal solution is Zero. /∆mixV=$\displaystyle 0$
SolutionsIdeal and Non-ideal SolutionsUnderstandcase_studymedium
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CBSE Class 12 Chemistry past-paper question from the 2025board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.