Acid, Base and Salts RRB PYQ

Acidic salts are salts that form an acidic solution when dissolved in water. They are typically formed when a strong acid partially neutralizes a weak base. Sodium Carbonate (Na2CO3) and Sodium Acetate (NaC2H3O2) are both salts of strong bases (NaOH and NaHCO3, respectively) and weak acids (H2CO3 and CH3COOH, respectively); since the base is strong, it completely reacts with the acid, and no acidic hydrogen atoms remain in the salt, so they are not acidic. Ammonium Phosphate (NH4PO4) can be formed by the partial neutralization of phosphoric acid (H3PO4), a weak acid, with ammonia (NH3), a weak base. Since the acid is weak, it doesn't fully react with the base, leaving some acidic hydrogen atoms (H+) in the salt, making ammonium phosphate acidic.

During the electrolysis of brine (a concentrated solution of NaCl), hydrogen gas (H2) is produced as a byproduct. Hydrogen burns with a distinctive pop sound when ignited. This process also produces chlorine gas (Cl2) and sodium hydroxide (NaOH). In the chlor-alkali industry, hydrogen is often combined with chlorine to produce hydrochloric acid (HCl).

The chemical formula for baking soda is NaHCO3, not CaSO4·(1/2)H2O (which corresponds to a different compound, Plaster of Paris). Baking soda is commonly used in cooking, cleaning, and neutralizing odors, but it is not typically used for making toys, materials for decoration, or smoothing surfaces. Its primary use is in neutralizing acids and basic cleaning tasks, making both statements incorrect.

A solution with blue-green colour is formed due to the formation of copper (II) chloride. When dilute hydrochloric acid (HCl) is added to copper (II) oxide (CuO), a blue-green solution of copper (II) chloride (CuCl2) is formed.

The pH value increase from 7 to 14 represents an increase in OH- ion concentration. pH scale measures the alkalinity and acidity of water soluble substances. The pH value increase from 0 to 7 represents anything acidic.

Red cabbage leaves act as a natural acid-base indicator (i-c) because they contain anthocyanin, which changes color in response to pH. Methyl orange is a synthetic acid-base indicator (ii-b) commonly used in titrations. Onion and clove are olfactory indicators (iii-a), as their smell can help detect the presence of acids or bases.

The correct raw materials for washing soda preparation are NaCl, NH3, and CO2. Washing soda (sodium carbonate, Na2CO3) is produced using the Solvay process. In this process, ammonia, carbon dioxide, and sodium chloride are used to produce sodium carbonate along with by-products. The ammonia is recovered and recycled, making the Solvay process both efficient and economical.

Sodium bicarbonate is used to neutralize excess acid in the stomach. Sodium bicarbonate acts as an antacid, helping to relieve conditions like acid reflux, heartburn, and indigestion. Sodium carbonate is known as washing soda, while sodium bicarbonate is known as baking soda. Sodium carbonate is used as a cleaning agent and in glass, paper, and soap industries.

Lemon juice has a pH of around 2.2 (i-c), gastric juice is highly acidic with a pH of 1.2 (ii-b), milk of magnesia has a basic pH of around 10 (iii-d), and sodium hydroxide solution is very basic with a pH of 14 (iv-a). The pH scale ranges from 0 to 14, where lower values indicate acidity, and higher values indicate basicity. Hence the correct match is (i)-c, (ii)-b, (iii)-d, (iv)-a.

Baking soda is manufactured using the Solvay process, which involves common salt (sodium chloride), carbon dioxide, and ammonia. These compounds react to form sodium bicarbonate (baking soda) through a series of reactions, ultimately producing the final product used for cooking, cleaning, skincare, fire extinguishing, and relieving heartburn by neutralizing acid.