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Differences Between Ideal and Non-ideal Solution

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Last updated date: 17th Apr 2024
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What are Ideal and Non-ideal Solutions?

Chemical reactions are fundamental processes that occur when substances interact with one another, leading to the formation of new substances. In chemistry, reactions can be categorised as ideal or non-ideal based on several factors, including efficiency, yield, and adherence to theoretical principles.


It is important to note that the classification of reactions as ideal or non-ideal is not always straightforward. Many reactions fall into a spectrum between these two extremes, exhibiting characteristics of both ideal and non-ideal behaviour. Factors such as reaction conditions, catalysts, reactant purity, and the presence of inhibitors or promoters can influence the extent to which a reaction aligns with the ideal or non-ideal criteria.


Characteristics of Ideal and Non-ideal Solutions

Ideal Solutions

Ideal reactions are characterised by several key features. Firstly, they exhibit high efficiency, meaning that they proceed to completion, converting all the reactants into products. This implies that the reaction goes in the desired direction with no competing side reactions or undesired byproducts. The reactants and products involved in ideal reactions follow stoichiometry precisely, adhering to the balanced chemical equation. Additionally, ideal reactions proceed at a reasonable rate, neither too slow nor too fast, allowing for convenient control and optimisation.


Furthermore, ideal reactions often display high yield. A high yield indicates that the reaction proceeds with minimal loss and waste, maximising the production of the desired product. Ideal reactions are also characterised by excellent selectivity, meaning they produce the desired product without forming significant amounts of other undesired compounds.


Non-ideal solutions

Non-ideal reactions deviate from these ideal characteristics. They may exhibit lower efficiency, resulting in the incomplete conversion of reactants to products. Non-ideal reactions may be subject to competing side reactions or the formation of byproducts, reducing the overall yield of the desired product. These side reactions can arise due to factors such as impurities in reactants, high temperatures, or the presence of catalysts that favour alternative pathways.


Non-ideal reactions deviate from these ideal characteristics. They may exhibit lower efficiency, resulting in the incomplete conversion of reactants to products. Non-ideal reactions may be subject to competing side reactions or the formation of byproducts, reducing the overall yield of the desired product. These side reactions can arise due to factors such as impurities in reactants, high temperatures, or the presence of catalysts that favour alternative pathways.


Furthermore, non-ideal reactions may exhibit slower reaction rates, requiring extended reaction times or the use of elevated temperatures or pressures to achieve acceptable conversion levels. Conversely, some non-ideal reactions may proceed too quickly, resulting in difficulties in controlling and manipulating the reaction parameters.


Ideal Solutions 

Non-Ideal Solutions

They show high efficiency 

They show reduced efficiency

Converts all reactants into products

Partial/Incomplete conversion of reactants to products 

No side reactions or by products

Have side reactions and unwanted byproducts

High yield 

Reduced yield

High selectivity 

Low selectivity 


Ideal and Non-Ideal Solution Differences 

An ideal solution is a theoretical concept that assumes perfect mixing between two or more components.


  • No Interactions: Ideal solutions assume that there are no interactions between the molecules or ions of the solute and solvent. This means that the solute-solute, solvent-solvent, and solute-solvent interactions are all equal. As a result, the behaviour of the solution is solely determined by the concentrations of the components.

  • Raoult's Law: Ideal solutions obey Raoult's law, which states that the vapour pressure of each component (element) in the solution is directly proportional to the mole fraction in the solution. This implies that the vapour pressure of the solvent and solute can be calculated based on their respective mole fractions.

  • No Volume Changes: Ideal solutions assume that there are no volume changes upon mixing. In other words, the volumes of the solute and solvent components are additive, without any significant changes due to interactions between them.


Non-ideal solutions deviate from these assumptions and exhibit different behaviour. Non-ideal solutions can be categorised into two main types:


Positive Deviations: A non-ideal solution exhibits positive deviations from ideal behaviour when the interactions between the components are stronger than those assumed in an ideal solution. This results in an increase in the vapour pressure of the solution compared to what is predicted by Raoult's law. Positive deviations are often observed when the solute-solvent interactions are stronger than the solute-solute and solvent-solvent interactions. Examples of positive deviations include solutions of ethanol and water or acetic acid and water.


Negative Deviations: Conversely, a non-ideal solution displays negative deviations from ideal behaviour when the interactions between the components are weaker than those assumed in an ideal solution. This leads to a decrease in the vapour pressure of the solution compared to the predictions of Raoult's law. Negative deviations are frequently observed when the solute-solute and solvent-solvent interactions are greater than the solute-solvent interactions. An example of a negative deviation is the solution of chloroform and acetone.


It is important to note that the concept of ideal and non-ideal solutions is an idealization used to simplify calculations and understand the behaviour of solutions in chemistry. In reality, most solutions exhibit some degree of non-ideal behaviour. However, the concept of ideal solutions provides a valuable framework for understanding and predicting the properties of solutions based on their component interactions.


Property

Ideal Solutions 

Non-Ideal Solutions

Interactions 

No 

Yes

Obey’s Raoult’s Law

Yes

No

Volume Changes

No

Yes

Deviations 

No

Can be positive or negative


Conclusion 

Ideal reactions in chemistry are characterised by high efficiency, complete conversion of reactants to products, excellent selectivity, and high yield. Non-ideal reactions, on the other hand, deviate from these ideal features, exhibiting lower efficiency, incomplete conversion, reduced yield, along with unwanted side reactions or byproducts. Chemists must understand these differences between ideal and non-ideal reactions to optimise reaction conditions, design catalysts, and develop strategies to improve the efficiency and selectivity of various chemical processes.


Ideal and non-ideal solutions differ based on their adherence to certain assumptions. Ideal solutions assume no interactions between components, obey Raoult's law and do not exhibit volume changes upon mixing. Meanwhile, non-ideal solutions do not follow these assumptions and can display positive or negative deviations. Understanding the differences between ideal and non-ideal solutions is essential for accurately predicting the behaviour and properties of solutions in various chemical processes.

FAQs on Differences Between Ideal and Non-ideal Solution

1. What are ideal and non-ideal solutions?

Ideal solutions assume the following - no interactions between components, obey Raoult's law and do not exhibit volume changes upon mixing.


However, Non-ideal solutions deviate from these assumptions and can display either positive or negative deviations.

2. What are some of the characteristics of ideal and non-ideal solutions?

Characteristics of ideal solutions are - they exhibit high efficiency, high selectivity, and excellent yield.


Characteristics of non-ideal solutions are low efficiency, incomplete conversion of reactant to products, low yield, and unwanted side reactions and byproducts.

3. What are the two types of non-ideal solutions?

Ideal solutions can be categorised into positive and negative deviations.