Question

100 ml of liquid A was mixed with 25 ml of liquid B, to give a non-ideal solution of A-B. The volume of the mixture will be:
A) 75ml
B) 125ml exact
C) Fluctuating between 75 ml to 125 ml
D) Close to 125 ml but not exceed than 125 ml

Answer 1

For an ideal solution volume change after mixing is zero. Non-ideal solutions show a negative deviation to volume change after mixing. Let us find the answer to this question by using this concept.

Complete answer:
We have given 100ml of liquid A and 25 ml of liquid B. After mixing they give a non-ideal solution of A-B.
The volume change of non-ideal solution after mixing that is {\text{\Delta }}{{\text{V}}_{{\text{mix}}}} is less than zero.
{\text{\Delta }}{{\text{V}}_{{\text{mix}}}} < 0{\text{ (non ideal solution)}}
If we add a volume of liquid A and a volume of liquid B we will get
Volume of liquid A + Volume of liquid B = 100 ml +25 ml = 125 ml
However, as stated above non-ideal solution negative deviation to volume change after mixing. This negative deviation to volume change is due to an increase in the magnitude of the intermolecular force of attraction in solution. Due to an increase in the intermolecular force of attraction volume of the mixture decreases slightly. In option (A) volume of the mixture is given 75 ml which is very less. So, option (A) is incorrect.
The volume change of the ideal solution after mixing that is {\text{\Delta }}{{\text{V}}_{{\text{mix}}}} is equal to zero.
{\text{\Delta }}{{\text{V}}_{{\text{mix}}}} = 0
So, the volume of mixture given in option (B) 125 ml is incorrect as the resulting mixture given to us is non- ideal. Thus, option (B) is incorrect.
In option (C) it is given, fluctuating between 75 ml to 125 ml it is also incorrect.
As the volume of non- ideal solutions decreases slightly it should be close to 125 ml but not exceed than 125 ml.

Thus, the correct option is (D) Close to 125 ml but not exceed than 125 ml.__

Note: The main difference between ideal and non-ideal solution is in case of ideal solution volume change of mixture is zero and in the case of non-ideal solution volume of the mixture decreases slightly. So, a non-ideal solution has a negative value of {\text{\Delta }}{{\text{V}}_{{\text{mix}}}}.