Acids, Bases, and Salts: Chemical Reactions and Properties

Posted on May 8, 2024 in Chemistry

Why Should Curd and Sour Substances Not Be Kept in Brass and Copper Vessels?

Solution:

Curd and sour food substances contain acids, which can react with the metals in brass and copper vessels. This reaction can release harmful substances into the food, potentially causing health problems.

Reaction of Acids with Metals

Solution:

When an acid reacts with a metal, it typically produces a salt and hydrogen gas. For example:

Metal + Acid → Salt + Hydrogen gas

Gas Evolved from Metal Compound A

Solution:

Since the gas evolved extinguishes a burning candle and calcium chloride is formed, the gas is likely carbon dioxide (CO₂). Therefore, metal compound A is likely calcium carbonate (CaCO₃). The balanced chemical equation for the reaction is:

CaCO₃(s) + 2HCl(aq) → CaCl₂(aq) + CO₂(g) + H₂O(l)

Acidic Character in Aqueous Solutions

Solution:

The acidic character of a substance in an aqueous solution is determined by its ability to release hydrogen ions (H⁺). Acids like HCl and HNO₃ readily dissociate in water, producing H⁺ ions. Compounds like alcohol and glucose, while containing hydrogen, do not release H⁺ ions in water and therefore do not exhibit acidic properties.

Electrical Conductivity of Acidic Solutions

Solution:

Aqueous solutions of acids conduct electricity due to the presence of charged particles called ions. When acids dissolve in water, they dissociate into H⁺ and corresponding anions, allowing the solution to carry an electric current.

Effect of Dry HCl Gas on Litmus Paper

Solution:

Dry HCl gas does not change the color of dry litmus paper because it does not release H⁺ ions in the absence of water. The acidic behavior of HCl is only observed in aqueous solutions.

Diluting an Acid

Solution:

When diluting an acid, it is crucial to add the acid to water slowly and with stirring. Adding water to a concentrated acid can generate a large amount of heat, potentially causing the solution to splatter and leading to burns. The correct method ensures a controlled release of heat and minimizes the risk of accidents.

Effect of Dilution on Hydronium Ion Concentration

Solution:

Diluting an acidic solution decreases the concentration of hydronium ions (H₃O⁺) per unit volume. While the total number of H₃O⁺ ions remains the same, they become dispersed in a larger volume of water, reducing their concentration.

Effect of Excess Base on Hydroxide Ion Concentration

Solution:

Adding excess base to a solution of sodium hydroxide initially increases the concentration of hydroxide ions (OH^–). However, there is a limit to the solubility of the base. Once the solution becomes saturated, adding more base will not further increase the OH^– concentration.

Comparing pH and Hydrogen Ion Concentration

Solution:

A lower pH value indicates a higher hydrogen ion concentration. Therefore, solution A with a pH of 6 has a higher H⁺ concentration and is acidic, while solution B with a pH of 8 has a lower H⁺ concentration and is basic.

Influence of H⁺ Ions on Solution Nature

Solution:

The concentration of H⁺ ions determines the nature of a solution. Higher H⁺ concentration results in an acidic solution, while lower H⁺ concentration leads to a basic solution.

Presence of H⁺ Ions in Basic Solutions

Solution:

Basic solutions do contain some H⁺ ions, but their concentration is significantly lower than that of hydroxide ions (OH^–). The dominance of OH^– ions is what makes the solution basic.

Treating Acidic Soil

Solution:

Farmers treat acidic soil with substances like quicklime (calcium oxide), slaked lime (calcium hydroxide), or chalk (calcium carbonate) to neutralize the excess acidity and raise the pH level, making the soil more suitable for crop growth.

Common Name of CaOCl₂

Solution:

The common name for CaOCl₂ is bleaching powder.

Substance Yielding Bleaching Powder

Solution:

Bleaching powder is produced by treating calcium hydroxide with chlorine.

Sodium Compound for Softening Hard Water

Solution:

Sodium carbonate (washing soda) is commonly used to soften hard water by removing calcium and magnesium ions, which cause hardness.

Heating Sodium Hydrocarbonate

Solution:

Heating sodium bicarbonate (NaHCO₃) produces sodium carbonate (Na₂CO₃), water (H₂O), and carbon dioxide (CO₂) gas:

Reaction of Plaster of Paris with Water

Solution:

When Plaster of Paris (CaSO₄.1/2H₂O) reacts with water, it forms gypsum (CaSO₄.2H₂O):

CaSO₄.1/2H₂O + 3/2H₂O → CaSO₄.2H₂O