Acids, Bases and Salts

Solution

Acids have several distinct chemical properties. They react with metals to produce hydrogen gas, for example, zinc reacts with hydrochloric acid to form zinc chloride and hydrogen gas. Acids also react with metal carbonates and hydrogencarbonates to produce carbon dioxide, water, and a salt, such as the reaction between hydrochloric acid and sodium carbonate. Additionally, acids turn blue litmus red, have a sour taste, and conduct electricity in aqueous solutions due to the presence of H+ ions. They neutralize bases to form salt and water, a reaction known as neutralization. For instance, hydrochloric acid reacts with sodium hydroxide to produce sodium chloride and water. Acids also react with metal oxides to form salt and water, like the reaction between sulfuric acid and copper oxide.

Solution

Neutralization is a chemical reaction where an acid and a base react to form salt and water. This reaction is exothermic, releasing heat. For example, when hydrochloric acid (HCl) reacts with sodium hydroxide (NaOH), they neutralize each other to form sodium chloride (NaCl) and water (H2O). The general equation is Acid + Base → Salt + Water. This reaction is crucial in various applications, such as in antacids that neutralize excess stomach acid. Another example is the treatment of acidic soil with lime (calcium hydroxide) to neutralize the acidity. The pH of the resulting solution is 7 if the acid and base are of equal strength, indicating a neutral solution.

Solution

The pH scale is a numerical scale ranging from 0 to 14 used to measure the acidity or alkalinity of a solution. A pH of 7 is neutral, below 7 is acidic, and above 7 is alkaline. The scale is logarithmic, meaning each unit represents a tenfold difference in hydrogen ion concentration. Acids with a pH close to 0 are strong acids, while those near 7 are weak acids. Similarly, bases with a pH near 14 are strong bases, and those closer to 7 are weak bases. The pH can be measured using pH paper or a pH meter. For example, lemon juice has a pH of about 2, making it acidic, while soap has a pH of about 10, making it alkaline. The pH scale is essential in various fields, including medicine, agriculture, and environmental science.

Solution

Acids react with most metals to produce hydrogen gas and a salt. For example, when magnesium reacts with hydrochloric acid, it forms magnesium chloride and hydrogen gas. The general reaction is Acid + Metal → Salt + Hydrogen gas. Bases, on the other hand, react with certain metals like aluminum and zinc to produce hydrogen gas and a salt. For instance, sodium hydroxide reacts with zinc to form sodium zincate and hydrogen gas. These reactions are important in industrial processes, such as the production of hydrogen gas and the extraction of metals from their ores. However, not all metals react with acids or bases; noble metals like gold and platinum do not react.

Solution

Bleaching powder, chemically known as calcium oxychloride (CaOCl2), is formed by the action of chlorine gas on dry slaked lime (Ca(OH)2). The reaction is Ca(OH)2 + Cl2 → CaOCl2 + H2O. Bleaching powder is a white powder with a strong smell of chlorine. It is used for bleaching cotton and linen in the textile industry, bleaching wood pulp in paper manufacturing, and disinfecting drinking water. It also acts as an oxidizing agent in chemical industries. Bleaching powder releases chlorine when treated with dilute acids, which is responsible for its bleaching and disinfecting properties. For example, when treated with hydrochloric acid, it releases chlorine gas, which bleaches colored substances by oxidation.

Solution

Indicators are substances that change color in the presence of acids or bases, helping to identify their nature. Natural indicators include litmus, turmeric, and red cabbage juice. Litmus turns red in acidic solutions and blue in basic solutions. Synthetic indicators like phenolphthalein and methyl orange are also commonly used. Phenolphthalein is colorless in acidic and neutral solutions but turns pink in basic solutions. Methyl orange is red in acidic solutions and yellow in basic solutions. Indicators are used in laboratories and industries to determine the pH of solutions. For example, litmus paper is dipped into a solution to test its acidity or alkalinity. Universal indicator, a mixture of several indicators, gives a range of colors corresponding to different pH values.

Solution

Baking soda, or sodium hydrogencarbonate (NaHCO3), is prepared by reacting sodium chloride with water, carbon dioxide, and ammonia in the Solvay process. The reaction is NaCl + H2O + CO2 + NH3 → NH4Cl + NaHCO3. Baking soda is a white crystalline powder with a slightly salty taste. It is used in baking as a leavening agent, where it releases carbon dioxide when heated, making dough rise. It is also used in antacids to neutralize excess stomach acid, in fire extinguishers, and as a cleaning agent. When heated, baking soda decomposes to form sodium carbonate, water, and carbon dioxide: 2NaHCO3 → Na2CO3 + H2O + CO2. This property is utilized in baking and fire extinguishers.

Solution

Water of crystallization refers to the fixed number of water molecules present in the crystalline structure of a salt. These water molecules are loosely bound and can be removed by heating. For example, copper sulfate crystals (CuSO4.5H2O) contain five water molecules per formula unit. When heated, they lose water and turn white, forming anhydrous copper sulfate. Rehydrating anhydrous copper sulfate restores its blue color. Another example is gypsum (CaSO4.2H2O), which loses water to form plaster of Paris (CaSO4.½H2O) when heated. Water of crystallization affects the physical properties of salts, such as color and shape. It is essential in various applications, including the preparation of plaster and the storage of certain chemicals.

Solution

pH plays a crucial role in various aspects of everyday life. In the human body, enzymes function optimally within a specific pH range; for example, stomach acid has a pH of about 1.5-3.5 for digestion. Soil pH affects plant growth, with most crops preferring a pH of 6-7. Acid rain, with a pH below 5.6, harms aquatic life and buildings. The pH of water is monitored to ensure it is safe for drinking. In agriculture, lime is added to acidic soil to neutralize it. pH is also important in food preservation, medicine, and industrial processes. For instance, antacids neutralize excess stomach acid, and pH-balanced shampoos maintain hair health. Understanding pH helps in maintaining health, environment, and industrial efficiency.

Solution

Acids react with metal carbonates and hydrogencarbonates to produce salt, carbon dioxide, and water. For example, hydrochloric acid reacts with sodium carbonate to form sodium chloride, carbon dioxide, and water: Na2CO3 + 2HCl → 2NaCl + H2O + CO2. Similarly, sodium hydrogencarbonate reacts with hydrochloric acid to produce sodium chloride, water, and carbon dioxide: NaHCO3 + HCl → NaCl + H2O + CO2. These reactions are used in fire extinguishers, where the carbon dioxide produced helps to smother fires. They are also used in baking, where carbon dioxide makes dough rise. The effervescence observed during these reactions is due to the release of carbon dioxide gas. These reactions are important in various industrial and laboratory processes.

Solution

Acids react with metals to produce salt and hydrogen gas. For example, Zn + H2SO4 → ZnSO4 + H2. With metal carbonates and hydrogencarbonates, acids produce salt, water, and carbon dioxide. For example, Na2CO3 + 2HCl → 2NaCl + H2O + CO2. These reactions are essential for understanding the neutralization process and the production of gases.

Solution

Strong acids have pH values less than 3, weak acids between 3 and 7, strong bases above 11, and weak bases between 7 and 11. The pH value indicates the concentration of H+ ions, affecting the solution's acidity or basicity.

Solution

Neutralization is the reaction between an acid and a base to form salt and water. An everyday example is using antacids (bases) to neutralize excess stomach acid (HCl), relieving acidity.

Solution

Acids and bases conduct electricity in aqueous solutions because they dissociate into ions (H+ and OH-), which are charge carriers. For example, HCl dissociates into H+ and Cl- ions in water.

Solution

The pH scale is crucial for maintaining the pH balance in soil for agriculture, in the human body for metabolic processes, and in water bodies for aquatic life. For example, acid rain with pH less than 5.6 harms aquatic ecosystems.

Solution

Bleaching powder (CaOCl2) is formed by the action of chlorine on dry slaked lime: Ca(OH)2 + Cl2 → CaOCl2 + H2O. It is used for bleaching, disinfecting water, and as an oxidizing agent.

Solution

Water of crystallization is fixed water molecules in a salt's crystal structure. For example, CuSO4.5H2O (blue vitriol) loses water on heating, turning white, and regains color upon adding water.

Solution

Plaster of Paris (CaSO4.1/2H2O) is prepared by heating gypsum at 373K: CaSO4.2H2O → CaSO4.1/2H2O + 1.5H2O. It is used for making casts, molds, and in construction.

Solution

Olfactory indicators change smell in acidic or basic media. For example, onion's smell disappears in a base but remains in an acid, indicating the nature of the solution.

Solution

The chlor-alkali process involves electrolysis of brine (NaCl solution) producing NaOH (used in soap, paper), Cl2 (disinfectants, PVC), and H2 (fuels, ammonia). The reaction is 2NaCl + 2H2O → 2NaOH + Cl2 + H2.

Solution

Natural indicators are eco-friendly and easily accessible but lack precision and consistency. Synthetic indicators, like phenolphthalein and methyl orange, offer precise pH measurements but are chemical-based and may pose environmental hazards. For example, turmeric changes color in basic solutions but cannot provide exact pH values, whereas phenolphthalein gives a clear color change at pH 8.3, making it suitable for precise titrations.

Solution

When a metal reacts with an acid, the metal displaces hydrogen from the acid, forming a salt and releasing hydrogen gas. This occurs because metals are more reactive than hydrogen. For example, zinc reacts with hydrochloric acid to form zinc chloride and hydrogen gas: Zn + 2HCl → ZnCl₂ + H₂↑. The evolution of hydrogen gas can be tested by bringing a burning candle near the gas, which produces a pop sound.

Solution

pH plays a crucial role in various biological and industrial processes. In biological systems, enzymes function optimally within a specific pH range; for instance, stomach enzymes work best at pH 2. In agriculture, soil pH affects nutrient availability. Industrially, pH control is vital in wastewater treatment to neutralize harmful acids or bases. Deviations from optimal pH can lead to enzyme denaturation or inefficient industrial processes.

Solution

Bleaching powder (CaOCl₂) is a strong oxidizing agent used for disinfecting water and bleaching textiles. It reacts with water to release chlorine. Baking soda (NaHCO₃) is a mild base used in cooking and antacids. When heated, it decomposes to release CO₂, making it useful in baking. Both are derived from sodium chloride but serve vastly different purposes due to their chemical properties.

Solution

Water of crystallization refers to water molecules chemically bonded to a salt's crystal structure. For example, copper sulfate pentahydrate (CuSO₄·5H₂O) appears blue due to these water molecules. Upon heating, the water is lost, turning the salt white. Rehydrating it restores the blue color. This water affects the salt's color, shape, and solubility.

Solution

Antacids like magnesium hydroxide neutralize excess stomach acid (HCl) to relieve acidity. The reaction is: Mg(OH)₂ + 2HCl → MgCl₂ + 2H₂O. Mild bases are preferred because strong bases can damage the stomach lining and cause alkalosis, a condition where the body's pH becomes too high.

Solution

The chlor-alkali process involves electrolyzing brine (NaCl solution) to produce chlorine gas, hydrogen gas, and sodium hydroxide: 2NaCl + 2H₂O → 2NaOH + Cl₂ + H₂. Chlorine is used for disinfectants and PVC, hydrogen for fuels and ammonia, and sodium hydroxide in soap and paper industries.

Solution

Acid rain results from sulfur and nitrogen oxides reacting with water vapor, forming sulfuric and nitric acids. It damages aquatic life, soil fertility, and buildings. Mitigation includes reducing fossil fuel combustion, using scrubbers in industries, and promoting renewable energy. For example, limestone can neutralize acidic lakes.

Solution

Metal carbonates react with acids to produce salt, water, and CO₂. In soda-acid fire extinguishers, sodium bicarbonate reacts with sulfuric acid: 2NaHCO₃ + H₂SO₄ → Na₂SO₄ + 2H₂O + 2CO₂. The CO₂ smothers the fire by displacing oxygen.

Solution

Plaster of Paris (CaSO₄·½H₂O) is prepared by heating gypsum (CaSO₄·2H₂O) at 373K. When mixed with water, it rehydrates to form gypsum, hardening into a solid mass: CaSO₄·½H₂O + 1½H₂O → CaSO₄·2H₂O. It is used for casts, molds, and construction due to its quick-setting property.