Definition of Strong Acids and Weak Acids With Examples

In order to know about the weak and strong acids one must know the basics of an acid. So basically the question remains that what does an acid called? So in the ordinary words acid is basically a chemical element that can be dissolved in water and can give H+ ions in the solution or you can say that the element that can be able to react with base and produce water and salt is called acid. According to the definition that scientist Lewis have given us so far is that when a chemical substance is able to give protons, so that it can accept a pair of electrons is called acid and this acid called Lewis acid and the substance that releases pair of electrons is called Lewis base.

Acid substances turn the blue litmus into red and it takes part in reaction with some basic metals (e.g. iron, silver, zinc etc.).  There are several acids available out there which is used every day by chemical labs and classrooms. The acids like sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid is called the minerals acids which have inorganic compounds in it. And the organic acids like carboxylic acid, sulfonic acid and phenols have organic compounds in it. All these acid substances includes at least one hydrogen atom in it and when it dissolves in water it gives H+ ion to the solution according to the Arrhenius theory.

 

Arrhenius Theory

Arrhenius theory was introduced to us in 1887 by Swedish scientist Savante Arrhenius. And according to this theory acid substances dissolves in water to produce electrically yield molecules called ions. In this case we have known before that acid gives H+ ions to the solution but the fact is that H+ (hydrogen ion) cannot exist in water alone. When Acids come to the water it produces OH (hydroxide ions) and this ion exists in water in a combined state with water molecule as hydronium ion( H3O+). For making it remembered easily hydronium ion is referred as the hydrogen ion. The acidic behavior of such acids like (e.g. sulfuric, nitric, hydrochloric, acetic acids) is justified by their ability to produce hydrogen and hydroxide ions continuously in solution. Such acids may called as strong and weak acids depending on the production rate of hydrogen ion and hydroxide ions comparatively in the solution.

Definition of Strong Acids

Strong acid is that particular substance which easily dissolved in water and completely disassociate into their ions into the solution. Yielding one or more protons as per molecule. There are only 7 common strong acids that are used.

  • HCl – hydrochloric acid
  • HNO3 – nitric acid
  • H2SO4 – sulfuric acid ( HSO4 is known as a weak acid)
  • HBr – hydrobromic acid
  • HI – hydroiodic acid
  • HCLO4 – perchloric acid
  • HCLO3 – chloric acid

Examples of ionization of weak acids:

  • HCl → H+ + Cl
  • HNO3 → H+ + NO3
  • H2SO4 → 2H+ + SO42-

 

Definition Of Weak Acids

Weak acids are those substances which does not completely dissolve in water and partially disassociate into their ions and give fewer protons to the solution rather than a strong acid. For example HF is a weak acid and it disassociates into H+ and F ions into the water but some HF molecules remains in the water as constant particle so HF is not a strong acid. There are more strong acids than weak acids. Most of the organic acids are the weak acids. Here I am gonna put a list below mentioning some of the weak acids.

  • HCOOH – formic acid
  • HF – hydrofluoric acid
  • HCO2H – methanoic acid
  • HSO4 – hydrogen sulfate ion
  • H2SO3 – sulfurous acid
  • C6H5COOH – benzoic acid
  • CH3COOH – acetic acid
  • H3PO4 – phosphoric acid
  • HO2C2O2H – oxalic acid
  • HNO2 – nitrous acid

Example of disassociation of a weak acid ethanoic acid to produce hydroxonium cations  and ethanoate anions.

                                         CH3COOH + H2O    ——–>    H3O+ + CH3COO

Ionization of Weak Acids

While describing the ionization process of the weak acids someone might have question in their mind that why the reaction symbol of a strong acid ionizing in water is a simple arrow facing towards left to right. But in the case of explaining the disassociation of a weak acid the reaction symbol is double arrow? It basically indicates that both the forward reaction and reverse reaction occur at the equilibrium of the solution. At the equilibrium the weak acid, its conjugate base and the hydrogen ion all are present in the solution. The general reaction of the ionization of a weak acid could be like this

                                                                       H3COOH ⇌ CH3COO + H+

The acetate ion is the conjugate base of the acetic acid.

Reason of Being Weak of the Weak Acids

The ionization rate of the acid in the solution is completely depends on the polarity or the distribution of the electrons in a chemical bond. When two atoms in a bond have nearly same electro-negativity values, the electrons in the bond are fifty-fifty shared and spend equal time regarding their atoms. And in the other hand when it is shown that there is a significant difference of electro-negativity values in the atoms there occurs a separation of charge and as a result electrons present in a bond is mostly taken by a certain atom than the other atom.

Hydrogen atoms gather slightly positive charge when it gets bonded to an electro-negative element. If there is less electron density regarding to a hydrogen atom then it becomes easier to get ionized and the molecule becomes more acidic. Weak acids basically take the formation when there is less polarity presented between the hydrogen atom and the other atom and that doesn’t allow the easy removal of the hydrogen ion.

Another factor that affects the strength of an acid is the size of the atom according to the size of the hydrogen atom. If the size of the atom increases then the strength of the bond decreases so that it becomes really easy to break the bond and release the hydrogen ion and increases the strength of the particular acid.

Commercial Production of Various Acids

HYDROCHLORIC ACID

IUPAC NAME: Chlorane

OTHER NAMES: Muriatic acid, hydronium chloride, spirits of salt, Chlorhydric acid

APPEARANCE: colorless, transparent, liquefied, blows out into the air when concentrated.

PRODUCTION: Hydrochloric acid was historically invented form rock salt which is now chemically similar to the reaction of NaCl and Sulfuric acid (H2SO4)

                                                 2 NaCl +H2SO4 ——–>  2HCl + Na2SO4

SULFURIC ACID

IUPAC NAME: Sulfuric acid

OTHER NAMES: Oil of Vitriol

APPEARANCE: Colorless, without smell and a viscous liquid that can be dissolved in water and can be synthesized in reactions that are highly exothermic

PRODUCTION: the main method to produce sulfuric acid is called the contact process. Here sulfur dioxide (SO2) is used mainly and meanwhile four main steps are used in this process in which the sulfur dioxide and oxygen make with the catalyst.

  1. S + O2     ——–>   SO2      
  2. SO2 + ½ O2  ——–>   SO3
  3. SO3 + H2SO4 ——–>   H2S2O7
  4. H2S2O7 + H2O ——–>   2 H2SO4

NITRIC ACID

IUPAC NAME: Nitric Acid

OTHER NAMES: Aqua fortis, Spirit of Niter, Hydrogen Nitrate, Acidum Nitricum

APPEARANCE: Highly corrosive mineral acid

PRODUCTION: the industrial production of nitric acid had been started from 1905 with Birkeland- Eyde process. The nitric acid manufacture process basically involves two stages.

  1. Oxidation of ammonia
  2. Absorption of nitrogen oxides
  • Oxidation of ammonia

This method includes the oxidation of ammonia to nitric oxide

                                     4NH3 + 5O2——–>  4NO + 6H2O + ΔH = -900 kJ/mol

This process highly requires high pressure, excess air, a catalyst and high temperature.

  • Absorption of nitrogen oxides

In this process the gases are cooled in temperature below 42o C. and then the air is added and the gases compressed again. The temperature rises up to 162o C. the additional compression and the cooling aid the reactions, moving the following equation

                                              2NO + O2 ——–>  2NO2    ΔH = -115 kJ/mol

                                              2NO2  ——–> N2O4        ΔH = -58 kJ/ mol

The gases then pass through one or more tanks to meet the stream of water, which is flowing in the opposite direction of the gas. In this step the oxidation of the nitrogen monoxide continues and the adsorption finally reaches out in the formation of nitric acid.

                                   3N2O4 + 2H2O ——–>   4HNO3 + 2NO + ΔH = -103 kJ/mol

ACETIC ACID

IUPAC NAME: acetic acid

OTHER NAMES: vinegar, hydrogen acetate, methanecarboxylic acid

APPEARANCE: colorless, liquefied and pungent smell

PRODUCTION:  acetic acid can be produced both synthetically and by fermentation of bacteria. All over the world 75% of acetic acid is produced just to use in the chemistry labs. Most of the acetic acids use to produced by the process of methanol carbonation . In his particular process methanol and carbon monoxide react with each other to produce acetic acid as per the equation mentioned below. this process includes iodomethane as an intermediate.

                                               CH3-OH + CO   ——–>  CH3-COOH

This process basically occurs in three different steps mentioned below.

                                              CH3OH + HI    ——–>   CH3I + H2O

                                                   CH3I + CO      ——–>     CH3COI

                                         CH3COI + H2O   ——–>  CH3COOH + HI

PHENOL

IUPAC NAME: phenol/benzenol

OTHER NAMES: carbolic acid, phenylic acid, phenic acid and hydroxybenzene

APPEARANCE: crystalline solid, colorless, smells like ammonia

PRODUCTION: phenol have been occurred a great industrial value in the world of chemistry. And for this huge importance of phenol, it is manufactured by several processes throughout the world. But the only process that can be done technically is called the cumene process and the methods of this process follow the equation mentioned below.

                           C6H6 + CH3-CH2=CH2 + O2  ——–> C6H5OH + CH3-CO-CH3

FORMIC ACID

IUPAC NAME: Formic acid

OTHER NAMES: hydrogen carboxylic acid, carbonous acid, matacarbonic acid, hydroxy methane, formylic acid.

APPEARANCE: colorless, liquefied, pungent smell, miscible with water.

PRODUCTION: in this chemical industry formic acid has a separate importance according to the usage in the chemistry labs for various experiments. The inorganic process of manufacturing formic acid is quite easy this process follows the equation mentioned below.

Methanol and carbon monoxide reacts with each other in the presence of strong base produce methyl formate.

                                                     CH3OH + CO  ——–>  HCO2CH3

Then the produced methyl formate goes through the process of hydrolysis which requires a large amount of water. Then methyl foramte reacts with ammonia and produce formamide. Later this is hydrolyzed to produces formic acid.

                                       HCO2CH3 + NH3 ——–>  HC-O-NH2 + CH3OH

                         2HC-O-NH2 + 2H2O + H2SO4  ——–>  2HCOOH + (NH4)2SO4

In the information that has been given above that there are two different types of acids available out there and they have their own pros and cons. Strong and weak both acids are very important to be known to for chemistry classes and labs. Both the weak and strong acids react differently with their reactants. So the easiest way to remember their characteristics anyone can just read out the explanation we have mentioned above. Here I am gonna mention some basic important points over strong acids so that one can easily identify the difference between strong and weak acid.

  • When strong acid gets dissolve in water it completely breaks into their ions in the solution. While weak acids partially disassociate into their ions in the solution.
  • PH is something that is used in explaining the concentration of hydrogen ions in solution. Strong acid like hydrochloric acid is mostly used in the chemistry labs nowadays. It has the PH rate around to 0 to 1. The more ph rate decreases of a particular acid the concentration of hydrogen ion in solution increases. Here I am gonna mention the basic formula of measuring PH of an acid.

                                                         PH= -log10[H+]

  • There are only 7 strong acids available and rests of the acids are known as weak acid. And hese acids are hydrochloric acid, nitric acid, sulfuric acid, hydrobromic acid, hydroiodic acid, perchloric acid and chloric acid.

Final Words

So this is all about the facts and nature of the strong and weak acids mentioned above. If you look for any information regarding strong and weak acids then the information given above should be followed. We will keep updating this post and renewing the facts of the different acids. Acids has become a huge portion of the experiments in the chemistry labs nowadays so everyone should know each and everything about acids.

If you have any further query about this specific topic then let us know through the comment sections below. We will help you out at your earliest.

 

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