Properties of acids and bases - class-XI

Oxalic acid H2C2O4 is a diprotic acid. The first dissociation (H2C2O4 → HC2O4- + H+) is easier than the second (HC2O4- → C2O4²- + H+) because removing H+ from a negatively charged species (HC2O4-) is harder. K2 is typically 1/1000 of K1.

When metal carbonate is treated with dilute hydrochloric acid, the products formed are salt, water and carbon dioxide.

When a metal carbonate reacts with an acid, it produces a salt, water, and carbon dioxide gas. The general equation is: Metal Carbonate + Acid -> Salt + Water + Carbon Dioxide.

Acids liberate sulphur dioxide or hydrogen sulphide on reaction with metallic sulphides.

Marble chips are made up of by calcium carbonate. When they are treated with $HCl$, carbon dioxide gas is formed along with water and calcium chloride. ${ CaCO } _{ 3 }+HCl\rightarrow { CaCl } _{ 2 }+{ H } _{ 2 }O+{ CO } _{ 2 }$

Carbonates contain carboxylate ion which reacts with mineral acids to form carbon dioxide gas which gets evolved from the reaction mixture.

$h = 0.03$, $C = 0.1 M$ , $K _{w} = 10^{-14}$       

BaCl2 + H2SO4 -> BaSO4 + 2HCl. One mole of BaCl2 reacts with one mole of H2SO4 to produce 2 moles of HCl. The remaining 1 mole of H2SO4 is also acidic. Total acid to neutralize is 2 moles of HCl + 1 mole of H2SO4 (which has 2 H+), totaling 4 moles of H+. Therefore, 4 moles of KOH are required.

Turmeric, purple cabbage juice (containing anthocyanin), and litmus paper all act as indicators which help us to detect whether a particular substance is acidic or basic.

An indicator is usually a weak acid or a weak base which changes colour in acidic or basic solutions.  The pigment anthocyanin present in the china rose flower makes its solution an indicator.
China rose solution gives dark pink colour with acid and green colour with base.

$Al _2O _3+KOH\rightarrow KAlO _2+H _2O$ 

Oxides and hydroxides of certain metals are amphoteric in nature.

Alkali reacts with hot concentrated caustic alkalies to give corresponding soluble salt and liberate hydrogen.

$2Al+2NaOH+2H _2O\rightarrow2NaAlO _2+3H _2$ and $2Al+2KOH+2H _2O\rightarrow2KAlO _2+3H _2$ 

$Pb+2NaOH\rightarrow Na _2PbO _2+H _2$ 

Gold,palladium,gallium are all noble metals which are dissolved in aqua regia. It is also known as royal water which is a mixture of hydrochloric acid and nitric acid in the ratio of 3:1 respectively.

Sulphuric acid is non flammable so soda acid is most common fire extinguisher. Carbon dioxide is liberated by the action of sulphuric acid on baking soda or sodium bicarbonate. This increases the percentage of carbon dioxide in air. Due to this the supply of air is cut off and fire is extinguished.

Sulphuric acid is diprotic acid and shows different properties depending upon its concentration. It is a strong acid and in concentrated form it has strong dehydrating and oxidising properties. It has large number of applications. In almost all industrial processes sulphuric acid is used,in production of lead acid batteries,production of fertilizers,in chemistry labs,petroleum refining and production of paper. So it is called as the king of all acids.

Sulphuric acid develops voltage from the chemical reaction produced when two unlike materials such as the positive and negative plates are immersed in the electrolyte a solution of sulphuric acid and water. In typical lead-acid battery the voltage is approx. 2 volts per cell for a total of 12 volts.