Salts and their Uses Questions in English

(B) Common salt $(NaCl)$ is a crucial raw material for various chemicals used in daily life and industry.
$1$. Washing soda $(Na_2CO_3 \cdot 10H_2O)$ is produced from $NaCl$ via the Solvay process.
$2$. Bleaching powder $(CaOCl_2)$ is produced by the action of chlorine gas (obtained from the electrolysis of brine, i.e., $NaCl$ solution) on dry slaked lime.
$3$. Baking soda $(NaHCO_3)$ is produced using $NaCl, NH_3, CO_2,$ and $H_2O$.
Slaked lime $(Ca(OH)_2)$ is produced by adding water to quicklime $(CaO)$, not from common salt.
Therefore, $(i), (ii),$ and $(iii)$ are correct.

(A) Sodium carbonate $(Na_2CO_3)$ is formed by the neutralization reaction between carbonic acid $(H_2CO_3)$ and sodium hydroxide $(NaOH)$.
Carbonic acid $(H_2CO_3)$ is a weak acid.
Sodium hydroxide $(NaOH)$ is a strong base.
Since the salt is derived from a weak acid and a strong base,the resulting salt is basic in nature,having a $pH$ greater than $7$.

(B) Tooth enamel is composed of hydroxyapatite,which is a crystalline form of calcium phosphate,$Ca_3(PO_4)_2$.
Calcium phosphate is a salt formed by the reaction of a strong base,calcium hydroxide $Ca(OH)_2$,and a weak acid,phosphoric acid $H_3PO_4$.
Since it is a salt of a strong base and a weak acid,its nature is basic.

(C) $NH_{4}Cl$ is a salt formed by the reaction of a strong acid $(HCl)$ and a weak base $(NH_{4}OH)$.
When $NH_{4}Cl$ dissolves in water, it undergoes hydrolysis.
The $NH_{4}^+$ ion reacts with water to produce $H_3O^+$ ions, which makes the solution acidic.
Since the solution is acidic, the concentration of $H^+$ ions increases, resulting in a $pH$ value of less than $7$ $(pH < 7)$.

(B) Washing soda is chemically known as sodium carbonate decahydrate $(Na_2CO_3 \cdot 10H_2O)$.
When dissolved in water, it undergoes hydrolysis.
Sodium carbonate is a salt of a strong base (sodium hydroxide, $NaOH$) and a weak acid (carbonic acid, $H_2CO_3$).
Due to the presence of a strong base, the resulting aqueous solution is basic in nature, which turns red litmus paper blue.

(A) When soil becomes too acidic,it is not suitable for the growth of plants.
To neutralize the acidity,farmers add basic substances to the soil.
Lime (calcium oxide or calcium hydroxide) is a basic chemical commonly used for this purpose.
It reacts with the excess acid in the soil to form neutral salts and water,thereby restoring the soil pH to a level suitable for plant growth.

(A) Soil acidity is often caused by the accumulation of hydrogen ions or the presence of acidic fertilizers.
To neutralize acidic soil,a basic substance is added.
Lime (calcium oxide or calcium hydroxide) is a common alkaline material used in agriculture to raise the $pH$ of the soil,effectively neutralizing the acidity.
Therefore,the correct option is $A$.

(B) Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate.
Its chemical formula is $CaSO_4 \cdot 2H_2O$.
When gypsum is heated at $373 \ K$,it loses water molecules and becomes calcium sulfate hemihydrate,which is known as Plaster of Paris $(CaSO_4 \cdot \frac{1}{2}H_2O)$.

(A) salt solution has a $pH$ greater than $7$ if it is a salt of a weak acid and a strong base.
$CH_3COONa$ is a salt formed from a weak acid (acetic acid,$CH_3COOH$) and a strong base (sodium hydroxide,$NaOH$).
When dissolved in water,it undergoes hydrolysis to form a basic solution,resulting in a $pH > 7$.
$NH_4Cl$ and $NH_4NO_3$ are salts of a strong acid and a weak base,resulting in an acidic solution $(pH < 7)$.
$NaCl$ is a salt of a strong acid and a strong base,resulting in a neutral solution $(pH = 7)$.

(B) salt formed by the neutralization of a weak acid and a strong base will be basic in nature.
$Na_{2}CO_{3}$ is formed by the reaction between carbonic acid $(H_{2}CO_{3})$,which is a weak acid,and sodium hydroxide $(NaOH)$,which is a strong base.
$NH_{4}Cl$ is formed from a weak base $(NH_{4}OH)$ and a strong acid $(HCl)$.
$NaCl$ is formed from a strong acid $(HCl)$ and a strong base $(NaOH)$.
$KNO_{3}$ is formed from a strong acid $(HNO_{3})$ and a strong base $(KOH)$.

(A) $NH_{4}Cl$ (Ammonium chloride) is formed by the neutralization reaction between $NH_{4}OH$ (Ammonium hydroxide) and $HCl$ (Hydrochloric acid).
$NH_{4}OH$ is a weak base,while $HCl$ is a strong acid.
Therefore,$NH_{4}Cl$ is a salt of a strong acid and a weak base.

(C) hygroscopic substance is one that absorbs moisture from the atmosphere.
Anhydrous calcium chloride $(CaCl_2)$ is a well-known drying agent (desiccant) because it readily absorbs water vapor from the air,making it hygroscopic.
Cryolite,Feldspar,and Slag do not possess this property under normal atmospheric conditions.

(C) Copper carbonate $(CuCO_3)$ is a chemical compound that appears as a green-colored powder or salt. It is commonly found in nature as the mineral malachite. Therefore,the correct color of copper carbonate salt is green.

(C) The chemical formula of sodium sulfite is determined by the valency of its constituent ions.
Sodium $(Na)$ has a valency of $+1$.
The sulfite ion $(SO_{3}^{2-})$ has a valency of $-2$.
To balance the charges,two sodium ions are required for every one sulfite ion.
Therefore,the formula is $Na_{2}SO_{3}$.

(B) Oleum,also known as fuming sulfuric acid,is a solution of sulfur trioxide $(SO_{3})$ in sulfuric acid $(H_{2}SO_{4})$.
It is chemically represented as $H_{2}S_{2}O_{7}$,which is formed by the combination of $H_{2}SO_{4}$ and $SO_{3}$ $(H_{2}SO_{4} + SO_{3} \rightarrow H_{2}S_{2}O_{7})$.
Therefore,the correct chemical formula for oleum is $H_{2}S_{2}O_{7}$.