Difference Between Acid and Base

Acid and Base Introduction and Examples

Acid and base are the form of chemicals which plays a vital role in chemistry and are readily available in our daily life. Examples of acids include citric acid and lactic acid present in lemons and in dairy respectively. Some examples of bases include cleaning products like bleach and ammonia. Just about every liquid that we can think about in our day-to-day life are acid or base with the exception of water. Acid and base definition was evolved with the time through 3 sets of theories, which includes Arrhenius, Brønsted and Lewis theories. The substances which act as both acids and base are called as Amphoterism, water is the most common example of amphoterism, as it acts like both acid and base.

What is Acid?

According to Arrhenius, a substance can be said acid if they ionize or break-off in an aqueous solution to form hydrogen ions (H+ ions), this type of classification of acids can work for aqueous solutions. The limitation of this type of classification is that when both acids and bases react with each other then they will get neutralized as hydrogen ions and hydroxide ions react to produce water.

     H+ (aq) + OH- (aq) H2O (l)

According to Brønsted theory, a substance is said to be acid if they are donating a proton (Hydrogen ion donor). Brønsted did not go against the theory of Arrhenius, he just added to it. A compound that donates H+ ions is called as Brønsted-Lowry acid including typical acids, plus amines, and alcohol. This Brønsted-Lowry definition of an acid is the best definition acid can get.
According to Lewis theory, a substance is said to be acid if they are accepting electrons from the other substance included in the reaction. The outer shell of the acids gets complete after accepting the electron-pairs in their valence shell. There is no change in the oxidation state of the reaction including acids.

Properties of acids are as follows:

• Acids conduct electricity (i.e. they are electrolytes)
• They turn blue litmus to red
• Most of the acids are solid
• It has a sour taste
• They produce hydrogen after reacting with active metals like zinc, magnesium, aluminum or iron.
• Acids have a low pH value i.e. below 7.
• Salts and water are produced when an acid reacts with base or alkalis.
• Most of the acids are solids.
• Some of the acids can be said corrosive in nature.
• Weak and more volatile acids are replaced by strong and less volatile acids from their salts.

Types of acids are as follows:

Strong acids completely dissociate ions in water while weak acids partly dissociate ions in water. Acids are divided into 2 types based on the ion dissociation in water, i.e. strong acids and weak acids as stated below:-

1. Strong Acids- A strong acid completely dissociates ions in water. There are only 6 strong acids which are as follows:

• HCL (hydrochloric acid)
• HNO3 (nitric acid)
• HBr (hydrobromic acid)
• HI (hydroiodic acid)
• HClO4 (perchloric acid)
• HClO3 (chloric acid)

2. Weak Acids- A weak acid partly dissociates ions in water. The rest of the acids except for those 6 acids are weak acids. The hydrogen and halogen combine in a reaction to form a weak acid namely hydrofluoric acid, while hydrochloric acid is a very strong and extremely powerful and also corrosive in nature, but stated as weak acid.

What is Base?

A base is a chemical species that donates electrons, accept protons or release hydroxide (OH-) ions in aqueous solutions. There are certain characteristics displayed by the base that can be used to identify them. You can identify base with the help of these given ways like they are slippery to touch (e.g. soap), bitter in taste, react with acid to form a salt and catalyze certain reactions. It includes Arrhenius base, Bronsted-Lowry base and Lewis base as types of bases. There are some examples of bases such as alkaline metal hydroxides, alkaline earth metal hydroxide, and soap. 

Properties of base can be listed as follows:

• A base solution has pH balance more than 7.
• Bases have a bitter flavour so never try to taste it.
• When an aqueous base solution or molten bases solution is dissociated into ions they conduct electricity.
• Strong base reacts vigorously with acids and organic matter because these bases are caustic.
• Bases react in correct way with pH indicators. It turns litmus paper blue, methyl orange yellow and phenolphthalein pink whereas Bromothymol blue remains blue in the presence of a base. 

Types of bases

1. Strong base – It completely dissociates into its ions in water or in a compound that can remove a proton (H+) from a weak acid. Examples of strong base are sodium hydroxide (NaOH) and potassium hydroxide (KOH).
2. Weak Base- these bases completely dissociate in water. The aqueous solution is one of the examples that include a base and its conjugate acid.
3. Neutral base – It is the one that forms a bond with a neutral acid.
4. Superbase - This type of base is formed by alkali metal with its conjugate acid and even better in comparison to a strong base. One of the examples of the super base is sodium hydride (NaH).
5. Solid Base – It may be used in anion exchange resins or for reactions with gaseous acids. It is active in solid form. Silicon Dioxide (SiO2) and NaOH mounted on alumina are the examples of Solid base. 

Differences between Acid and Base 

Basis AcidBase
1. Arrhenius Definition Acid is a kind of chemical compound that when dissolved in water gives a solution with H+ ion activity more than purified water.A base is an aqueous substance that donates electrons, accept protons or release hydroxide (OH-) ions.
2. Bronstead Lowry DefinitionAn acid is a proton donor.While a base is a proton acceptor.
3. ExamplesAcetic acid (CH3COOH) and sulphuric acid are two examples of Acid.Sodium Hydroxide (NaOH) and Ammonia are two examples of Bases.
4. PH valuepH values of acid are less than 7.0.On the other hand, the pH value of base is greater than 7.0.
5. Phenolphthalein Acid remains colourless when dissolved.Bases make the solution turn pink when dissolved.
6. Chemical formula Acid starts with chemical formula H, for example, HCL (Hydrochloric Acid) but there is an exception of CH2COOH. At the same time, base has a chemical formula OH at the end of it. For example- NaOH (Sodium Hydroxide).
7. Litmus paper Acid turns blue litmus paper into red.Base turns red litmus paper into blue.
8. Strength Acid mainly depends on the concentration of the hydronium ions.Similarly happens in a base.
9. CharacteristicsAcid can be in the form of solid, liquid or gas form depending on the temperature.Bases have a bitter taste having a bit slippery and solid appearance except ammonia which is present in the gaseous state
10. DissociationWhen acids dissolved in water, it release hydrogen ions (H+).Base release hydroxide ions (OH-) when dissolved in water.
11. ExamplesExamples of acids are acetic acid, sulphuric acid, etc.Examples of bases are sodium hydroxide, ammonia, etc.