An Introduction to Acid and Base
Acid and base are the form of chemicals that play 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. 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 bases are called Amphoterism, water is the most common example of amphoterism, as it acts like both acid and base.
In the following article, we will discuss the definition of acids and bases and their properties, types as well as examples.
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What is Acid?
According to Arrhenius, a substance can be said to be acidic 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 Bronsted theory, a substance is said to be acid if they are donating a proton (Hydrogen ion donor). Bronsted did not go against the theory of Arrhenius, he just added to it. A compound that donates H+ ions is called Bronsted-Lowry acid including typical acids, plus amines, and alcohol. This Brønsted-Lowry definition of an acid is considered as the best definition of acid.
According to Lewis theory, a substance is said to be acidic 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 Acid
Some 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, aluminium 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 to be corrosive in nature.
Weak and more volatile acids are replaced by strong and less volatile acids from their salts.
Types of Acids
Strong acids completely dissociate ions in the water while weak acids partly dissociate into ions in water. Acids are mainly classified into 2 types based on the ion dissociation in water, i.e. strong acids and weak acids as stated below:-
Strong Acids- A strong acid completely dissociates ions in water. Some of the strong acids are as follows:
HCL (hydrochloric acid)
HNO3 (nitric acid)
HBr (hydrobromic acid)
HI (hydroiodic acid)
HClO4 (perchloric acid)
HClO3 (chloric acid)
Weak Acids- A weak acid partly dissociates ions in water. The rest of the acids except for some strong acids are weak acids. The hydrogen and halogen combine in a reaction to form a weak acid namely hydrofluoric acid, while hydrochloric acid is 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, accepts protons or releases hydroxide (OH-) ions in aqueous solutions. There are certain characteristics displayed by the base that can be used to identify them. You can identify bases 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. Arrhenius base, Bronsted-Lowry base and Lewis base are some different definitions of bases proposed by different scientists.. There are some examples of bases such as alkaline metal hydroxides, alkaline earth metal hydroxides, and soap.
Properties of Base
Some properties of bases are given below.
A base solution has a pH balance of more than 7.
Bases have a bitter flavour so never try to taste them.
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 the 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
There are different types of bases which are given below.
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 bases are sodium hydroxide (NaOH) and potassium hydroxide (KOH).
Weak Base – These bases completely dissociate in water. The aqueous solution is one of the examples that include a base and its conjugate acid.
Neutral Base – It is the one that forms a bond with a neutral acid.
Super Base – This type of base is formed by alkali metal with its conjugate acid and is even better in comparison to a strong base. One of the examples of the super base is sodium hydride (NaH).
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 examples of Solid bases.
The difference between acid and bases are listed below on the basis of different parameters.
Differences Between Acid and Base
Conclusion
Hence acids and bases are very important chemicals and they are identified by their chemical properties. The concept of acid and base is the basis of chemistry as these chemicals are used in different applications. In this article we learn about the properties, types and difference between acid and base.
FAQs on Difference Between Acid and Base
1. What is the definition of an acid and base?
There is a very famous Arrhenius concept based on which we can define acids and bases. According to Arrhenius's concept, acids are those compound that gives ${{H}^{+}}$ion on dissolving in the aqueous solution and thereby increases the concentration of ${{H}^{+}}$ions in the solution. While bases are those compound that gives $O{{H}^{-}}$ion on dissolving in the aqueous solution and increases the concentration of $O{{H}^{-}}$ions in the solution. For example, $HCl$ is an acid and $NaOH$ a base.
$HCl(aq.)\rightleftharpoons {{H}^{+}}+C{{l}^{-}}$
$NaOH(aq.)\rightleftharpoons N{{a}^{+}}+O{{H}^{-}}$
2. Write any $4$ properties that show the difference between acid and base?
Acids and bases are considered as the distinctive class of compounds as they show different physical and chemical properties.
Properties of acids:
(i) Acids produce ${{H}^{+}}$ions or ${{H}_{3}}{{O}^{+}}$ions in an aqueous solution.
(ii) They taste sour.
(iii) When they react with metal, hence producing hydrogen gas $({{H}_{2}})$.
(iv) Acids react with base and form a neutral salt compound from water.
Properties of bases:
(i) Bases produce $O{{H}^{-}}$ions in an aqueous solution.
(ii) They taste bitter.
(iii) When they react with metal like $Zn$,$Al$ produces hydrogen gas.
(iv) Bases react with acid, forming a salt from the water and losing their basicity.
3. What is the main difference between acid and base?
Some of the main differences between acids and bases are listed below:
Difference between an acid and a base
Basis | Acids | Bases |
Taste | Sour like taste | Bitter like taste |
Litmus paper | Turn blue litmus to red litmus | Turn red litmus to blue litmus |
Reaction with water | Forms ${{H}^{+}}$ions when reacts with water | Forms $O{{H}^{-}}$ions when reacts with water |
Phenolphthalein indicator | Phenolphthalein indicator remains colorless in an acidic solution. | The phenolphthalein indicator becomes pink in the basic solution. |
Examples | $HCl,\,{{H}_{2}}S{{O}_{4}},HN{{O}_{3}}$, lemon juice, etc | $NaOH,Ca{{(OH)}_{2}}$, lime water, etc |
There are many important facts on acids and bases available on the website Vedantu Difference Between Acid and Base, Where students can download as free PDFs.
4. Explain the ${{P}^{H}}$ difference between acid and base?
In chemistry ${{P}^{H}}$means the potential of hydrogen and it is a scale used to specify whether the aqueous solution is an acidic, basic, or neutral solution. This scale has values ranging from $0$to $14$ which ${{P}^{H}}=0$refers to the most acidic solution, ${{P}^{H}}=14$ refers to the most basic solution, and ${{P}^{H}}=7$specifies the neutral solution which means the solution is neither acidic nor basic. For the acidic solution, ${{P}^{H}}$the value ranges from $0-7$, and for the basic solution from $7-14$.
5. Is water an acid or a base?
Water is a compound with molecular formula ${{H}_{2}}O$ in which one oxygen molecule is covalently bonded with two hydrogen atoms. Water is an amphoteric molecule that can act both as an acid or base.
According to the Bronsted-Lowry concept, Water acts as an acid when it reacts with a base $N{{H}_{3}}$, donating an ${{H}^{+}}$ion to the base.
${{H}_{2}}O+N{{H}_{3}}\rightleftharpoons NH_{4}^{+}+O{{H}^{-}}$
Again water acts as a base when it reacts with the acid $HCl$, accepting ${{H}^{+}}$ions from the acid.
${{H}_{2}}O+HCl\rightleftharpoons {{H}_{3}}{{O}^{+}}+C{{l}^{-}}$
