[Chemistry Class Notes] on Acid and Base Reaction Pdf for Exam

1. A destructive is any hydrogen-containing substance that is prepared for giving a proton (hydrogen molecule) to another substance. A base is a molecule or molecule prepared to recognize a hydrogen molecule from a destructive force.

 

2. Acidic substances are normally recognized by their harsh taste. A destructive is basically a molecule which can give an H+ molecule and can remain energetically sure later an inadequacy of H+. Acids are known to become blue litmus red.

3. Bases, of course, are depicted by an unforgiving taste and a precarious surface. A base that can be separated in water is implied as a salt. Exactly when these substances misleadingly react with acids, they yield salts. Bases are known to become red litmus blue.

Destructive Definition Chemistry

• The term destructive and base have been described in different ways, dependent upon the particular point of view on properties of sharpness and basicity. Arrhenius at first described acids as blends which ionize to make hydrogen particles, and bases as combinations which ionize to convey hydroxide particles. According to the Lowry-Bronsted definition, a destructive is a proton promoter and a base is a proton acceptor.

• According to the Lewis definition, acids are particles or particles fit for arranging with unshared electron matches, and bases are iotas or particles having unshared electron sets open for proposing to acids. To be acidic in the Lewis sense, a molecule ought to be electron lacking. This is the broadest destructive base thought. All Lowery Bronstead acids are Lewis acids nevertheless, in like manner, the Lewis definition consolidates various reagents, for instance, boron trifluoride, aluminum chloride, etc

Theories of Acids and Bases

Three interesting speculations have been progressed to describe acids and bases. These theories fuse the Arrhenius speculation, the Bronsted-Lowry theory, and the Lewis theory of acids and bases. A short depiction of all of these speculations is given in this subsection. Acids and bases can be portrayed through three particular theories.

The Arrhenius speculation of acids and bases communicates that “a destructive makes H+ particles in a response however a base conveys an OH–molecule in its response”.

The Bronsted-Lowry speculation portrays “a destructive as a proton provider and a base as a proton acceptor”.

Finally, the Lewis significance of acids and bases portrays “acids as electron-pair acceptors and bases as electron-pair advocates”.

Also Check ⇒ Dilute Acids

PH of Acids and Bases

To notice the numeric worth of the level of destructiveness or basicity of a substance, the pH scale (wherein pH signifies ‘ability of hydrogen’) can be used. The pH scale is the most broadly perceived and trusted technique for assessing how acidic or crucial a substance is. A pH scale measure can change from 0 to 14, where 0 is the most acidic and 14 is the most key a substance can be.

Another technique for checking whether a substance is acidic or crucial is to use litmus paper. There are two kinds of litmus paper available that can be used to recognize acids and bases – red litmus paper and blue litmus paper. Blue litmus paper becomes red under acidic conditions and red litmus paper becomes blue under fundamental or stomach settling agent conditions.

Properties of Acids and Bases

1. Properties of Acids

• Acids are horrendous in nature.

• They are incredible transmitters of force.

• Their pH regards are reliably under 7.

• When reacted with metals, these substances produce hydrogen gas.

• Acids are cruel tasting substances.

• Models: Sulfuric destructive H2SO4, hydrochloric destructive HCl, acetic destructive CH3COOH.

 

Acid and base reaction play a major role in both industrial chemistry and biochemistry. Many substances we come across in our homes, supermarkets, and the pharmacy are either acids or bases.  Eg: aspirin and vinegar are acids and antacids are bases. Lemon is acidic in nature and Kiwi is alkaline. The taste in the food is also due to the presence of acids and bases in them. Before we discuss the characteristics of how do acids and bases react with each other and what is the reaction between acid and base,  let’s first understand What are Acids and Bases?

What are Acids and Bases?

We can define acids as substances that dissolve in water to produce H+ ions, it is capable of donating a proton (hydrogen ion) to another substance, whereas bases are defined as substances that dissolve in water to produce OH– ions and is a molecule or ion able to accept a hydrogen ion from an acid.

 

The general properties of acids and bases were known to people for more than a thousand years. The definitions of acid and base have changed dramatically as scientists have learned more about them.

 

Acids are usually identified by their sour taste. An acid is basically a molecule that can donate H+ ions and can remain favorable even after losing H+ions. Acids turn blue litmus red. On the other hand, A base is any substance that had a bitter taste, felt slippery to the touch, and caused color changes of red litmus paper to blue.

 

We encounter reactions between acid and base in our everyday lives. The orange, lemon, or grapefruit juice we drink contains citric acid. When milk is left, sometimes it turns sour, it contains lactic acid. The vinegar used contains acetic acid. According to this, a chemical bond is made by an acid-base combination. The properties of a molecule can be understood more easily by classifying them into acid and base fragments.

Theories of Acids and Bases

Three different theories define acids and bases. These different theories include the Arrhenius theory, the Bronsted-Lowry theory, and the Lewis concepts of acids and bases. A brief description of each of these theories with acid and base reaction examples are described below:

 

1. The Arrhenius Definition of Acids and Bases: 

• The first person to give detail about acids and bases was the Swedish chemist Arrhenius. According to his definition, An acid is a substance that dissolves in water to produce H+ ions and a base is a substance that dissolves in water to produce hydroxide (OH–) ions. 

HCl(g)  →  H+(aq) + Cl– (aq)     (HCl is Arrhen
ius acid)

NaOH(s)  → Na+ (aq) + OH– (aq)     (NaOH is Arrhenius base)

• Although Arrhenius’s ideas were widely accepted, it successfully explains the reaction between acids and bases that yield salts and water.

• The limitation in Arrhenius’s definitions of acids and bases is that it fails to explain how substances lacking hydroxide ions form basic solutions when dissolved in water, Eg: NO2— and F—.

• The reaction between ammonia (a base) with gaseous HCl (an acid) to give ammonium chloride is not an acid base reaction examples because it does not involve  H+  and  OH— :

NH3(g) + HCl(g) → NH4Cl(s)

  2. Properties of Bases

• A couple of properties, like a serious taste, are asserted by all bases. The bases feel precarious, also. Dream on what precarious cleaning agent takes after. What’s more, this is a foundation. Plus, when immersed in water, bases lead power since they involve charged particles in the course of action.

• They are found to have a frothy surface when reached.

• These substances release hydroxide particles (OH–particles) when separated in water.

• In their liquid courses of action, bases go probably as incredible conductors of force.

• The pH regards connecting with bases are reliably more unmistakable than 7.

• Bases are brutal tasting substances which can become red litmus paper blue.

• Models: Sodium hydroxide NaOH, milk of magnesia Mg (OH)₂, calcium hydroxide Ca (OH)₂.

3. Impartial Substances

• The impartial substance is a substance which has no destructive or base properties, has a comparable proportion of hydrogen and hydroxyl particles, and doesn’t adjust the shade of the litmus surface.

• These substances don’t show any acidic or principal credits.

• Their pH regards assessed to 7.

• Unprejudiced substances do not affect red or blue litmus paper.

• The pH of pure water is overall 7.

• Models: Water, Common salt (NaCl)

 

4. The Bronsted–Lowry Definition of Acids and Bases

• Because of some limitations in the Arrhenius definition, a more general definition of acids and bases was required. According to Bronsted and Lowry, A Bronsted acids undergo dissociation to yield protons and therefore increase the concentration of H+ ions in the solution, and A base is defined as a proton acceptor (or H+ ion acceptor) by this theory. The Bronsted–Lowry definition of an acid is the same as the Arrhenius definition, except that it is not restricted to aqueous solutions only. The Bronsted–Lowry definition of a base is far more general because the hydroxide ion is just one of many substances that can accept a proton. An advantage of the Bronsted-Lowry definition of acids and bases is its ability to explain the acidic or basic nature of an ionic species.

• The main limitation of  Bronsted–Lowry theory is that it fails to explain how compounds lacking hydrogen exhibit acidic properties, Eg: BF3 and AlCl3.

 

5. Lewis Concept of Acids and Bases

• According to Lewis’s concept of an acid, it states that it is a species that has a vacant orbital and therefore, has the ability to accept an electron pair, and A Lewis base can hold a lone pair of electrons and can act as an electron-pair donor.

• Lewis acids are electrophilic in nature and Lewis Bases are nucleophilic in nature.

• A Lewis acid can accept an electron pair from a Lewis base and forms a coordinate covalent bond in the process. The theory does not involve the hydrogen and hydroxide atoms in its definition of acids and bases.

• Lewis acids: Cu2+, BF3, Fe2+ ,Fe3+, Lewis bases: F–, NH3,AlCl3 ,C2H4.

• The major advantage of this concept is that many compounds can be defined as acids and bases. However, it does not focus on the strength of acids and bases.

• The major drawback of this theory is that it fails to explain the acid and base reaction that does not involve the formation of a coordinate covalent bond.

 

Difference Between Acid and Bases

 

The pH of Acids and Bases

• It is clear from the above discussion that the nature of the solution (acidic, basic, or neutral) can be represented in terms of either hydrogen ion concentration of hydroxide ion concentration, but it is convenient to express the acidity or basicity of a solution by referring to the concentration of hydrogen ions only.

•  pH measurement is done using pH paper and pH meter, The hydrogen ion concentration is expressed in terms of the numerical value of negative power to which 10 must be raised. This numerical value of negative power is termed pH, pH= -log [H+]  .

• The pH of a solution is defined as the negative logarithm of the concentration (in mol per liter) of hydrogen ions which it contains or the pH of the solution can be defined as the logarithm of the reciprocal of H+ ion concentration. Acids have a pH value less than 7, bases have a pH value greater than 7 and neutral solutions have a pH equals to 7.

Importance of pH in Everyday Life

• When the pH of rainwater is less than 5.6, it is acid rain.

• Our body works well within a pH range of 7.0 to 7.8.

• Our stomach produces HCl that helps in the digestion of food without harming the stomach. Sometimes excess acid is produced in the stomach that causes indigestion. To get rid of this, antacids (bases) are used.

 

Natural Indicators

Natural Indicators can be found naturally and they help in determining whether the substance is acidic or basic in nature. Turmeric, grape juice, Red cabbage, curry powder, cherries, beetroots, onion, etc are some of the examples of natural indicators.

 

Some flowers like hydrangeas can also help in determining the acidity or basicity of the soil. These flowers change color to blue if the soil is acidic in nature, purple if the soil is neutral, and pink if the soil is basic in nature. The intensity of the color is dependent on the amount of acid or base present in the soil. Soil that is highly acidic has deep blue flowers, whereas soil which is highly basic yields deep pink flowers.

 

Uses of Acids 

Sulphuric Acid: 

It  is Called as King of Chemicals. Some of Its Major Uses Are:

• It is used in manufacturing paints, drugs, dyes, and to produce fertilizers.

• It is used in car batteries.

• Used in the manufacturing of hydrochloric acid and alum.

Hydrochloric Acid: 

• It is also used for cleaning sinks and sanitary ware.

• It is used in various industries that use heating applications.

• It is applied to remove deposits from the boilers.

Acetic Acid:

• It is used as a cleansing agent in products like cleaning windows, floors, utensils, etc.

• It is used for enhancing the flavor of food. Acetic acid is commonly known as vinegar.

• This acid helps to remove stains on woodwork such as furniture and carpets.

Phosphoric Acid:

Citric Acid: 

Ascorbic Acid:

Boric Acid:

• It is widely used in detergents.

• Used in the manufacturing of glass, leather, paper, adhesives, and explosives.

 

Aqua Regia: 

It is a mixture of concentrated nitric acid and hydrochloric acid. It is highly corrosive and is able to attack gold and other resistant substances. It can be used to clean glassware, It is also used to remove noble metals such as gold, platinum, and palladium from the substrate.

 

Uses of Bases

Here are the some uses of Bases

Magnesium Hydroxide :

Calcium Hydroxide:

• It is an important ingredient in whitewash and mortar.

• It is also used in the preparation of dry mixes for painting and decorating.

• Used to neutralize the acidity in soils.

• Used to make bleaching powder.

 Sodium Hydroxide:

• It is occasionally used to unblock drains in the home.

• It is the key ingredient in the manufacture of soaps and detergents.

• It is also used in the manufacture of paper, textiles, and detergents.

• It is used in the refining of petroleum.

Ammonium Hydroxide:

• It is used to make fertilizers, raions, plastics, and dyes.

• It is used as a reagent in a chemical laboratory.

 

Acid and Base Reaction

When an acid is reacted with a base, salt and water are produced. The reaction between an acid and a base is termed a neutralization reaction. We will look at a few acid base reaction equations:

HCl (aq) + NaOH (aq) → NaCl (aq) + H2O (l)

HBr (aq) + KOH (aq) → KBr (aq)  + H2O (l) 

HCl (aq) + NH3(aq)  → NH4Cl (aq)