Ideal Solution: Definition, Characteristics and Importance

Ideal solution can be referred to as a homogeneous mixture where the molecular interaction between solution and solvent is identical to the molecular interaction of each component itself. 

Keyterms: Solutions, homogeneous mixture, molecular interaction, solvent, component, boiling point, vapour pressure, freezing point, colligative properties

---

Ideal Solution Definition

[Click Here for Sample Questions]

When two homogeneous mixtures of two or more than two components are combined, they form what is called a solution. The solvent, which is the highest quantity of a component, works towards determining the physical state of the solution. Two components mixed to form a solution is called a binary solution and the properties that this solution has are expressed in terms of its boiling point, vapour pressure, freezing point along with other colligative properties.The binary liquid in liquid solutions can be classified into two types ideal and non-ideal solutions. 

An ideal solution can be referred to as a mixture where the molecules belonging to various species are differentiable. The molecules present in an ideal solution apply forces on one another. When those forces are similar in case of all the molecules irrespective of their species, the solution is known as an ideal solution. 

Also Read:

---

Characteristics of an Ideal Solution

[Click Here for Previous Year Questions]

At most times, an ideal solution has the kind of physical properties that are very closely related to those of the pure components. Some of them are as follows: 

1. The enthalpy of a solution is zero. In case the enthalpy of the solution is closer to zero then it is more likely to show an ideal behaviour. Δ_mixH=0
2. The volume of mixing is also zero. Δ_mixV=0

In order to obtain an ideal solution, mixing a solvent and a solute that consists of a similar molecular size and structure can help. One can even take two substances X and Y, and then mix them. It can be seen that there are several intermolecular forces that exist between them.

Although getting a well balanced and stable ideal solution is a rare situation, sometimes some solutions tend to exhibit ideal behaviour. 

For example, 

• X and X experience intermolecular forces of attraction.
• Y and Y experience intermolecular forces of attraction.
• X and Y experience intramolecular forces of attraction.

Here, when the intermolecular forces of attraction are the same or equal, it gives us an ideal solution. It is extremely significant to understand the concept of an ideal solution, more so in situations where colligative properties and chemical thermodynamics are concerned. 

---

Comparison between Ideal Solution and an Non-Ideal Solution

[Click Here for Sample Questions]

---

The Physical Origin of Ideal Solution 

[Click Here for Previous Year Questions]

The ideality for gasses are very similar to that of the solutions. One of the most important differences however is that the intermolecular interactions in these liquids are quite strong and they cannot simply be neglected, the way they can for ideal gasses. However, it is not wrong to assume that the mean strength of these interactions are the same between each and every molecule of this particular solution.

---

Raoult's law 

[Click Here for Sample Questions]

Raoult’s law is followed in an ideal solution at majorly all the levels of temperatures and concentrations. The simplest definition of an ideal solution can be stated by calling it a homogeneous solution that is a place for the interaction between solute and solvent, the molecules of components.

It is a mixture in which the molecules of several different species are quite distinguishable, however, unlike the ideal gas, the molecules in this ideal solution exerts forces on one another. When those forces are the same for all molecules that are independent of species, then only is a solution referred to as ideal. 

---

Importance of Raoult's Law

[Click Here for Previous Year Questions]

In a hypothetical scenario, if one has a locked container that is loaded with volatile liquid A. For some time, owing to evaporation, few vapour particles might begin to form. As time passes, the A vapor particles will be in dynamic equilibrium with the liquid particles that are on the surface. The pressure exerted by the vapor particles of A at some given temperature is known as the vapor pressure of A at the same temperature.

When two homogeneous mixtures of two or more than two components are combined, they form what is called a solution. The solvent, which is the highest quantity of a component, works towards determining the physical state of the solution. Two components mix to form a solution that is called a binary solution and the properties that this solution has are expressed in terms of its boiling point, vapour pressure, freezing point along with other colligative properties. 

---

Things to Remember

1. Ideal Solutions is a part Class 12 chemistry first term syllabus.
2. It comes under Unit 2 Solution and carries a total of 8 periods and 4 to 5 marks.
3. Raoult's law states that when a non-volatile electrolyte is dissolved in a solvent the relative lowering of the vapour pressure is equal to the mole fraction of the solute”.
4.  When in a solution the interaction of different components of molecules does not differ from the interactions of the component’s of each molecule, it is called the ideal solution. It consists of the concentrations and temperatures that obey Raoult’s law.
5.  Two of the characteristics of an ideal solution are:

1. The mixing volume change should be zero.
2. The mixing heat change should be zero

Read More:

---

Previous Year Questions (PYQs)

• The mass of one mole of a substance in grams is called its…
• The mass of CaCO3 is required to react with 25 mL of…
• The number of moles of water present in 180gm of water… (AIIMS 1996)
• 4 g of a hydrated crystal of formula AxH2O has 0.8 g of water… (KCET 2013)
• The number of moles of KMnO4 that will be needed to react… (NEET 2007)
• The number of gram molecules of oxygen in 6.02 x 1023… (NEET 1990)
• The mole fraction of benzene in a solution containing… (COMEDK UGET 2012)
• One mole of NaCl contains 6.023 x 10 molecules of sodium…
• Equal moles of different substances contain the same number of…
• The density of 2 M aqueous solution of NaOH is 1.28 g… (NEET 2019)
• Find out the molecular weight of the substance. (Kb​forsolventis2.16∘C)...(NEET 1999)
• 1 M and 2.5 litre NaOH solution mixed with another 0.5 M and 3 litre NaOH solution. Then find out molarity of resultant solution : -...(NEET 1980)
• The molar mass of protein will be (R=0.083Lbarmol−1K−1):...(NEET 2011)
• A 0.1 molal aqueous solution of a weak acid is 30% ionized. If Kf​ for water is 1.86∘C/m, the freezing point of the solution will be -..(NEET 2011)
• If Kf​ and Kb​ for water are 1.861.86 and 0.512Kkg mol−1 the above solution will freeze at..(NEET 2005)