What are Acids and Bases?
Acids are chemical substances which are characterized by a sour taste in an aqueous medium. They have the tendency to turn blue litmus red. On the other hand, bases are chemical substances which are characterized by a bitter taste and are slippery to the touch. Some bases are soluble in water while others are not.
Water soluble bases are known as alkalis. They have the tendency to turn red litmus blue. Acids and bases react with a wide range of chemical compounds to form salts. Some chemical reactions of acids and bases are:
Physical Properties of Acids and Bases
The physical properties of acids and bases are listed in the table below.
|Colour||Mineral acids are colourless liquids but sometimes sulphuric acid becomes yellow due to impurities. Some organic acids are white coloured solids.
Examples: benzoic acid
|Bases are colourless except the hydroxides of iron and copper.|
|Solubility||Soluble in water||Some bases are soluble in water.|
Physical Properties of Acid
- The word “acid” comes from the Latin word for sour. This distinguishable property helps identify acids from other compounds such as salt and bases. Many acids can be hazardous if ingested and shouldn’t be tasted.
- Once the acid binds to the base, it becomes a neutral substance. Often this reaction can lead to water and salt. This is often seen when strong acids react with strong bases.
- The acids are driving electricity. Outside this, the batteries are used to produce electricity. The acid that conducts electricity strongly is a strong acid, and the acid that conducts electricity weakly is a weak acid.
Chemical Properties of Acid and Bases
1. Reactions of Acids and Bases with Metals
When a metal reacts with an acid, it generally displaces hydrogen from the acids. This leads to the evolution of hydrogen gas. The metals combine with remaining part of acids to form a salt. For example reaction of sulphuric acid with zinc.
\(H_2SO_4 ~+~ Zn ~\rightarrow ~ZnSO4 ~+ ~H_2\)
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.
\(2~ NaOH~ +~ Zn ~\rightarrow~ Na_2ZnO_2 ~+~ H_2\)
2. The Reaction of Metal Carbonates/Metal Bicarbonates with Acids
Metal carbonates/metal bicarbonates react with acids to produce salt, carbon dioxide and water. For example the reaction of sodium carbonate/sodium bicarbonate with hydrochloric acid.
\(Na_2CO_3~ + ~HCl~ (aq)~\rightarrow ~2NaCl ~(aq)~ +~ H_2O (l)~ +~ CO_2\)
3. The Reaction of Metal Oxide with Acids
Metal oxides react with acids to produce salt and water. For example reaction of copper oxide and dilute hydrochloric acid.
\(CuO~ + ~2HCl ~\rightarrow~ CuCl_2 ~+~ H_2\)
4. 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)
\(CO_2 ~+ ~Ca~ (OH)_2~ \rightarrow~ CaCO_3 ~+ ~H_2O\)
5. The Reaction between Acids and Bases
Acids react with bases to produce salt and water. The reaction between acids and bases to give salts is known as neutralization reactions. For example the reaction of sodium hydroxide with hydrochloric acid.
\(NaOH ~+ ~HCl ~\rightarrow~ NaCl ~+ ~H_2O\)
Neutralization of Acid and Base
The reaction between an acid and a base invariably gives salt and water and is called neutralization. In a neutralization reaction, one H+ ion of acid is neutralized by one OH– ion is base. When all the H+ ions in the acidic solution are neutralized by the same number of OH– ions of basic solution, it is called complete neutralization. The relative amounts of acid and base required for complete neutralization depends upon the total number of H+ and OH– ions produced by the respective acid and base.
Comparative Study of Properties of Acids and Bases
A comparative study of properties of acids and bases is given below in table.
|Corrosive action on skin: All acids and some alkalies show corrosive action on skin as they form painful blisters when they come in contact with skin.||H2SO4 absorbs water from skin tissues. HNO3 reacts with skin proteins to form a pulp like mass. NaOH and KOH are called caustic soda and caustic potash, respectively due to their causticizing action on skin.|
|Reactions taking place between acids and bases: All acids react with alkalis (metal hydroxides) to form salt and water. The reaction of an acid with a base to form salt and water as the products is called neutralization.||2KOH + H2SO4 → K2SO4 + 2H2O
Ca(OH)2 + 2HNO3 → Ca(NO3)2 + 2H2O
Frequently Asked Questions – FAQs
What are the uses of acids?
It may also be used to store milk. Sulphuric acid is commonly found in batteries. Batteries used to power car engines usually produce this acid. The processing of explosives, dyes, paints and fertilizers requires the use of sulphuric acid and nitric acid.
What are two acid examples?
Acids are liquids that give up the concentration to hydrogen ions. There are many common acid substances: lemon juice (citric acid), vinegar (acetic acid), stomach acid, and soda pop (carbonic acid). Acids are typically ionic with a positive hydrogen ion attached to a negative anion.
What is acid base and salt with example?
The reaction of acid and base yields two products; water and an ionic compound known as salt. This type of reaction is called a neutralization reaction. For example, sodium hydroxide reacts with hydrochloric acid and forms sodium chloride and water.
How are the basic salts are formed?
Basic salts are formed by neutralization of a strong base and weak acid; for example, the reaction of sodium hydroxide (a strong base) with acetic acid (a weak acid) produces water and sodium acetate. The conjugate acid of the low base makes the salt acidic.
What are the properties of an acid?
When dissolved in water, acids taste acidic, conduct electricity and react with metals to create hydrogen gas. Some indicator compounds can be used to detect acids, such as litmus. Acids turn blue litmus paper into red. Acid strength is measured on a pH scale.
What are examples of acids?
Acids are substances in solution which give up Hydrogen ions. Acids, while releasing hydrogen gas, are corrosive to metals, have a pH between 0 and 6.9, and are sour to the taste. Acids are found in many substances: lemon juice (citric acid), vinegar (acetic acid), stomach acid, and soda pop (carbonic acid).
Is pure water basic or acidic?
H2O is an acid, as well as a base. Since pH is defined as the negative log of the concentration of hydrogen ions, pure water has a pH of 7 or neutral. Pure water is neutral, as the number of positive hydrogen ions produced is equal to the negative number.
What is a pure acid?
Pure acids (without water) are composed of covalent small molecules. When water is added, the pure acid molecules react with water to form ions, commonly referred to as “the ionized acid.” The pure acids are poor conductors of electricity. Due to the mobile ions present, acids diluted with water are considerably better conductors.
What are weak acids?
A weak acid is an acid that in an aqueous solution, or water, partially dissociates into its ions. By contrast, in water, a strong acid dissociates completely into its ions. A weak acid’s conjugate base is a weak basis whereas a weak base’s conjugate acid is a weak acid.
For detailed discussions on physical and chemical properties of acids and bases, please visit BYJU’S.