Acid Strength: Definition, Acid Strength Order, Trends & Factors
Acid strength is defined as the ability of an acid to lose its hydrogen ion. It may depend on various factors like the type of acid, nature of acid and properties of acid. The strength of an organic acid depends on substituent effects and the strength of an inorganic acid depends on the oxidation state of an atom. The strong acid may completely dissolve in any solution by losing its most concentrated ion whereas weak acid may partially dissociate with an undissociated solution or dissociated products in the solution. This may remain in equilibrium with each other.
This Story also Contains
- Factors Determining Acid Strength
- Factors Affecting Acid Strength
- Acid Strength Order
Factors Determining Acid Strength
The strength of an acid can be measured as the degree of dissociation of acids. Hence the strength of an acid mainly depends on two factors such as:
Polarity of H-A bond
Strength of H-A bond
Here polarity and strength are the major components on which the degree of dissociation depends. The greater the polarity of H-A bond, the stronger is acid and similarly, the weaker the strength of an H-A bond, the stronger the acid and vice versa. The acid strength can also be determined based on two other factors such as the “inductive effect” and the “effect of oxidation state”.
Factors Affecting Acid Strength
The factors affecting the acid strength are as follows:
The strength of an acid depends on the strength of the H and A bond. The weaker the bond the less energy is required to break the bond and hence the acid is considered as a strong acid.
The polarity plays a major role when we consider the acid strengths of the elements that are present in the same row of the periodic table.
The size of A also affects the acid strength, that is, as the atom becomes larger the bond becomes weaker and the acid strength increases.
The binding strength also plays a key role when we compare the acid strength of the elements that are in the same group on the periodic table.
Acid Strength Order
The acid strength order helps to determine the strength of the different acids and their order based on the elements and nature of the elements present in the periodic table. The order may be either ascending or descending order of the acid strengths of the different acids. The acid strength of hydrides of 17th group elements are in increasing order like HF<HCl<HBr<HI
Frequently Asked Questions (FAQs)
The main factor that determines the acid strength is the dissociation constant. It is also used for determining the strength of the base. As the dissociation constant is more, the acid or base is stronger and vice versa. These two are directly proportional to each other.
The seven strong acids are Chloric acid, Hydrobromic acid, sulphuric acid, Hydrochloric acid, Hydroiodic acid, perchloric acid and nitric acid.
The factors that affect acidity are:
Charge of an atom
Role of an atom
Inductive effect
Resonance
Orbitals
Yes, we can determine the acid strength based on the pH(Potential of Hydrogen). The strength of acid increases with an increase in the ionization and a decrease in the pH)Potential of Hydrogen). That is when pH(Potential of Hydrogen) is more, acidity is less and vice versa.
The strength of acid increases with an increase in the number of terminal oxygen atoms and this occurs due to the inductive effect and also due to the increase in the stabilization of the conjugate base.