What are acid and base?
A molecule capable of creating a covalent bond with an electron pair is an acid. Acids are very commonly found in some of the foods we consume like, for example, citrus fruits such as oranges and lemons, which contain citric acid; vinegar contains acetic acid; in fact, our stomach uses hydrochloric acid for digestion. Acids have a sour taste. It reacts with metals to form hydrogen and reacts with carbonates to form a salt, carbon dioxide and water. Acids turn blue litmus paper red. Acid's strength can be measured on the pH. Acids are sticky and frequently cause nose burning.
In chemistry, a base can be defined in three ways as they are referred to as Arrhenius bases, Brønsted bases, and Lewis bases. But all the definitions state that bases are the substances that react with acids as originally proposed by G.-F. Rouelle in the mid-18th century. In the year 1884, Svante Arrhenius proposed that the base are the substances that dissociate in the aqueous solution to produce hydroxide (OH-) ions. These hydroxide ions then react with the hydrogen ions (H+) released from the dissociation of the base to form water in an acid-base reaction.
By altering the equilibrium of the self ionization of water, the solution that is yielded by the base has a very low amount of hydrogen ion activity as compared to that of hydrogen ion which is present in the pure water. Therefore water has a pH that is higher than 7 at the standard conditions. If the soluble base contains and releases the hydroxide ion quantitatively, it was referred to as alkali. Metal oxides, hydroxides, and especially alkoxides are basic, and conjugate bases of weak acids are weak bases.
Properties of Base
Physical properties of bases
They are considered as the distinctive class of the compounds because of their properties when they are in aqueous solution. The physical properties of acids are as follows:-
Acids in an aqua solution are known as electrolytes as they conduct electrical currents. Some acids are described as strong electrolytes because they completely dissociate in the water and yield a large number of ions. Other acids are considered weak acids because they cannot dissociate completely in water and yield fewer ions.
Acids have a sour taste. Vinegar lemon and other sour candies contain acid in them.
Once the acid is bound to the base it creates a neutral substance. Often the substance is water and salt. This is predominantly noticed when a strong acid reacts with a strong base. This happens because when one mole of acid reacts with an equivalent mole of base it neutralizes the base.
The colour of certain acid-base indicators ll is changed because of the presence of acid. Litmus and phenolphthalein are the two main indicators that are unknown. Blue litmus turns red due to the presence of acid. But unlike litmus paper, phenolphthalein turns colourless.
Chemical Properties of Acids:
Acids react with Reactive Metals Like the Followings:
Acid + metal → salt + hydrogen
Copper and silver do not react with dilute acids, for example,
2HCl(aq) + Mg(s) → MgCl2(aq) + H2(g)
Zn(s) + H2SO4 (aq) →ZnSO4 (aq) + H2(g)
Acids React with Bases
Acid + Base -> salt + water
6HNO3(aq) + Fe2O3(s) → 2Fe(NO3)3(aq) + 3H2O(l)
This is the reaction of acids and bases with metals.
Acids React with Carbonates
Acid + carbonate => any salt + water + carbon dioxide
H2SO4(aq) + CuCO3(s) →CuSO4(aq) + H2O(l) + CO2(g)
So these are the chemical properties of acids and bases
4. Acids React with Bases
Acid + Base -> salt + water
6HNO3(aq) + Fe2O3(s) → 2Fe(NO3)3(aq) + 3H2O(l)
This is the reaction of acids and bases with metals.
5. Acids React with Carbonates
Acid + carbonate => any salt + water + carbon dioxide
H2SO4(aq) + CuCO3(s) →CuSO4(aq) + H2O(l) + CO2(g)
Properties of Bases
Physical properties of bases
Bases are less present in the food but are present in many household products like that in cleaning products that contain ammonia which is a base. Sodium hydroxide is used as a drain cleaner. Antacids that are used to reduce the effect of the acids in the stomach are comprised of magnesium hydroxide or sodium hydrogen carbonate. Bases have properties that are in contrast with the acids in the majority. Thus few of the physical properties of bases are as follows:-
Aqueous Solution off base is also electrolyte in nature. Similar to that of the acid, bases can also be weak or strong electrolytes.
Bases are bitter in taste and are found in food less frequently than acids. Many of the bases are slippery in texture like that of soaps.
It also changes the colour of the indicator. The litmus paper turns blue in the presence of base while it turns phenolphthalein into pink.
Bases do not react with metals like that of acids.
Base react with acid to produce water and salt.
Chemical properties of Bases
Reactions of Bases with Metals
Alkalis (bases that are soluble in water) react with the metal to produce salt and hydrogen gas. For example reaction of zinc with sodium hydroxide.
NaOH (aq) + Zn(S) → Na2ZnO2 + H2(g)
The Reaction of Non-metal Oxide with Bases
Non-metal oxides react with bases to produce salt and water. For example the reaction of carbon dioxide and lime water (calcium hydroxide).
CO2 + Ca(OH)2 → CaCO3 + H2O
The Reaction between Acids and Bases
Acid + Base -> salt + water
6HNO3(aq) + Fe2O3(s) → 2Fe(NO3)3(aq) + 3H2O(l)
This is the reaction of acids and bases with metals.
Reactions between bases and water
The following reaction represents the general reaction between a base (B) and water to produce a conjugate acid (BH+) and a conjugate base (OH−):
B(aq) + H2O(l) ⇌ BH+(aq) + OH-(aq)
The equilibrium constant, Kb, for this reaction can be found using the following general equation:
Kb = [BH+][OH-]/[B]
Solved Examples
Question 1: What happens when you mix an acid and a base?
Solution: When an acid and a base are placed together, the process of neutralization takes place—acids and base's reaction causes the neutralization of the acid and base properties. Neutralization is a process when acid and base are combined together; salt and water are produced. Such as when NaOH reacts with HCl, the product formed is NaCl and H2O. Here, NaCl is salt.
Question 2: Are all bases alkaline in nature? Justify your answer.
Solution: The term 'alkaline' is usually used for basic solutions, but they are not meant to be the same. All bases are not alkaline because all bases are not soluble in water, and alkalis are best known as bases that dissolve in water to form hydroxyl ion (OH-), and all are Arrhenius bases. Usually, water-soluble alkalis, such as barium carbonate, become soluble in water only when they react with an acidic solution containing water. Bases are generally chemical substances that can accept H+ ions.
Fun Facts
We can identify an unknown chemical as an acid or base by using wet litmus paper. Litmus paper makes acid red and bases blue. A litmus paper is treated with an extract from a certain lichen that changes colour according to pH. Both acids and bases can neutralize each other. strong bases can have a slippery feeling. Vitamin c is also a kind of acid known as ascorbic acid.
FAQs on Properties of Acids and Bases
1. What is a strong acid?
When acid is marked as a strong acid, it actually does not matter how powerful and how corrosive it can be. The strength of acid actually refers to the ability to release hydrogen ions into a solution. Strong acids are one which completely dissociates into their ions into the water, which means all of their molecules break up in a settlement. Strong acids produce at least one hydrogen cation(H+) per molecule. We can identify weak acids like they will dissociate less than 1%, which indicates that very few of their units will break up to release a hydrogen ion.
2. Why are acids called proton donors?
Acids are chemical substances that donate H+ ions to bases. Since a hydrogen atom is an electron and a proton, so an H+ ion is just a proton; therefore, acid is a 'proton donor,' and a base is a 'proton acceptor.' The reaction between an acid and base is a proton transfer. Acids do not 'donate' hydrogen ions; they surrender them.
For example: HA(aq) + H2O(l) → H3O+(aq) + A-(aq)
The acid gives a proton (H) to the base (H2O) thus giving products of H3O (with an extra proton) and A- (without one proton deducted). Hence, acids are called proton donors.