Acid, Base and Salts RRB PYQ

Carbon dioxide gas is evolved when sodium carbonate reacts with hydrochloric acid. Chemical equation: Na2CO3 + 2HCl → 2NaCl + CO2 + H2O.

The reaction between magnesium hydroxide (Mg(OH)2) and hydrochloric acid (HCl) is a neutralisation reaction. In this reaction, an acid (HCl) reacts with a base (Mg(OH)2) to produce a salt (MgCl2) and water (H2O). This type of reaction is commonly seen in applications such as antacids and chemical processes.

The pH scale ranges from 0 to 14, where lower values indicate higher acidity. A solution with a pH of 0 is the most acidic, having the highest concentration of hydrogen ions (H+). Comparatively, solutions with pH values of 1, 2, and 6 are less acidic.

Acid rain refers to rainfall with a pH less than 5.6, making it more acidic than normal rainwater. Under natural conditions, pure rainwater is slightly acidic, with a pH of around 5.6 due to the presence of dissolved carbon dioxide forming weak carbonic acid. However, when harmful gases like sulfur dioxide (SO2) and nitrogen oxides (NO2) are released into the atmosphere—mostly from the burning of fossil fuels—they react with water vapor to form stronger acids such as sulfuric acid (H2SO4) and nitric acid (HNO3).

Nature of dry HCl gas is not acidic due to lack of water for dissociation of HCl into H+ and Cl-. Hence, blue or red litmus paper does not change its colour.

In the reaction Ca(OH)2 + A → CaCl2 + H2O, hydrochloric acid (HCl) acts as reactant A, reacting with calcium hydroxide to produce calcium chloride and water, exemplifying a neutralisation reaction. The balanced equation is: Ca(OH)2 + 2HCl → CaCl2 + 2H2O.

Plaster of Paris is made by heating gypsum (CaSO4·2H2O) to remove water, resulting in a white powder. It is widely used as a fireproofing material because it can withstand high temperatures without burning. Additionally, Plaster of Paris is used in construction for making casts, molds, and decorative elements. Its quick-setting property makes it ideal for various applications in both industry and art.

To neutralize excess acidity in the stomach, one can take antacids like Mg(OH)2, which act as mild bases to counteract the acid. Stomach acidity is caused by the overproduction of Hydrochloric Acid (HCl). Antacids are basic in nature and undergo a neutralization reaction with the acid to produce salt and water, thereby providing relief from irritation. The reaction between stomach acid and magnesium hydroxide is expressed as: Mg(OH)2 + 2HCl → MgCl2 + 2H2O. Magnesium hydroxide is commercially known as milk of magnesia. Other common antacids used for this purpose include sodium bicarbonate (baking soda) and aluminium hydroxide.

Aqueous solution of copper sulphate turns blue litmus red as it is acidic in nature. Litmus paper is made by an extract of lichen plant.

In this reaction, potassium hydroxide (KOH) and nitric acid (HNO3) are both aqueous solutions, and they react to form potassium nitrate (KNO3) in aqueous solution and water (H2O) in liquid form: 2KOH(aq) + 2HNO3(aq) → 2KNO3(aq) + 2H2O(l). This is a typical neutralization reaction, where an acid reacts with a base to form a salt and water.