Acid, Base and Salts RRB PYQ

When Babu heated dilute nitric acid at 70°C for about 10 minutes, the pH of nitric acid decreased. As temperature increases, the decomposition of acid increases, leading to more dissociation of hydrogen ions (H+), which lowers the pH, making the solution more acidic.

Baking powder is a mixture of baking soda (sodium bicarbonate) and a mild edible acid, such as tartaric acid. This combination helps release carbon dioxide when moistened, causing dough to rise and make baked goods light and fluffy.

When acid is mixed with water, it will increase the concentration of hydronium ions per unit volume. When an acid is mixed with water, it undergoes ionization releasing hydrogen ions. The H+ ions combine with water to produce hydronium ions. More acid results in more hydronium ions in solution, raising the hydronium ion concentration.

According to the Arrhenius definition, a base is a substance that increases the concentration of hydroxide ions (OH-) when dissolved in an aqueous solution. Formation of OH- can be shown as: NaOH(aq) → Na+(aq) + OH-(aq). Strong bases such as NaOH and KOH dissociate completely, releasing lots of OH-, while weak bases such as NH3 react with water to produce OH- only partially. Bases have a characteristic bitter taste and they feel slippery or soapy to the touch. Bases turn red litmus paper blue.

Ammonium chloride (NH4Cl) is formed when hydrochloric acid (HCl) reacts with ammonium hydroxide (NH4OH). This is an example of an acid-base reaction, where HCl (an acid) donates H+ ions, and NH4OH (a base) provides OH- ions, which combine to form the salt NH4Cl and water (H2O). The balanced reaction is: HCl + NH4OH → NH4Cl + H2O.

Baking powder is a leavening agent commonly used in baking. It typically consists of sodium bicarbonate (baking soda) and an acid, often cream of tartar or another acidic component. When moistened and heated, baking powder releases carbon dioxide gas, causing dough or batter to rise and become light and fluffy.

Copper (II) Chloride is produced when dilute hydrochloric acid is added to a beaker containing a small amount of copper oxide. This is an example of a neutralization reaction. Copper (II) oxide is a black solid whereas copper(II) chloride solution is blue-green.

Salt and water is always formed during a neutralization reaction between a strong acid and a strong base. When both the acid and base are strong, they dissociate completely in aqueous solution. The hydrogen ions from the acid combine with the hydroxide ions from the base to produce water, while the remaining ions combine to form a salt. Example: HCl (strong acid) + NaOH (strong base) → NaCl (salt) + H2O (water).

As the pH value increases from 7 (neutral) to 14 (highly alkaline), it indicates an increase in the concentration of hydroxide ions (OH-) and a corresponding decrease in hydrogen ion (H+) concentration.

Sodium hydroxide reacts with hydrochloric acid in a neutralisation reaction to form sodium chloride (table salt) and water: NaOH + HCl → NaCl + H2O. Sodium hydroxide is a strong base, while hydrochloric acid is a strong acid. Their reaction produces salt and water, therefore hydrochloric acid is the correct option.