Acid, Base and Salts RRB PYQ

Calcium carbonate is a chemical compound with the formula CaCO3. Limestone, chalk, and marble are different forms of calcium carbonate. It is commonly found in rocks as the minerals calcite and aragonite, notably in limestone, a sedimentary rock composed mainly of calcite. Calcium carbonate is a major component of eggshells, snail shells, sea shells, and pearls.

NH4+ and NH3 act as a conjugate acid-base pair. A conjugate acid-base pair consists of two species that differ by a single proton (H+). In this pair, NH4+ acts as the acid because it can donate a proton to become NH3, while NH3 acts as the base because it can accept a proton to reform NH4+. This relationship is often shown in equilibrium reactions, such as when ammonia dissolves in water.

Sodium bicarbonate is the chemical name for baking soda. Its chemical formula is NaHCO3. It is commonly used as a leavening agent in baking. When it reacts with acids in the batter, it releases carbon dioxide gas, which makes the batter rise and become fluffy. Apart from cooking, it is also used for cleaning, deodorizing, and in some medical treatments.

The pH value of pure water at 25°C is 7. This means that the concentration of hydrogen ions and hydroxide ions is equal in pure water, and there is no acidic or basic character. At 25°C, the concentration of both hydrogen ions and hydroxide ions in pure water is 1×10^-7 mol/L, resulting in a neutral pH of 7.

The chemical formula of bleaching powder is CaOCl2, also known as calcium hypochlorite. Bleaching powder is a widely used chemical compound known for its disinfecting and bleaching properties. It is commonly used in water treatment, household cleaning, and as a bleaching agent in the textile and paper industries. The typical reaction to produce bleaching powder involves the combination of chlorine gas with calcium hydroxide: 2Ca(OH)2 + 2Cl2 → Ca(OCl)2 + CaCl2 + 2H2O.

A chemical reaction occurs when we add hydrochloric acid to washing soda (sodium carbonate). The chemical equation for the reaction is: Na2CO3 + 2HCl → 2NaCl + H2O + CO2. The acid (HCl) reacts with the base (Na2CO3) to form a salt (NaCl), water (H2O) and carbon dioxide gas (CO2). The reaction releases carbon dioxide gas, which appears as bubbles and causes brisk effervescence, since carbon dioxide is a gas at room temperature and pressure and evolves rapidly, so excess gas escapes as bubbles.

The Contact Process is used for the manufacturing of sulphuric acid. Burning sulphur to form sulphur dioxide (SO2): S + O2 → SO2. Oxidation of SO2 to SO3 using a vanadium (V) oxide catalyst: 2SO2 + O2 → 2SO3. SO3 is absorbed in concentrated H2SO4 to form oleum, which is then diluted to make sulphuric acid.

A solution is neutral when the amount of hydrogen ions (H+) is equal to the amount of hydroxide ions (OH-). The pH scale goes from 0 to 14, and pH 7 is the neutral point, where H+ and OH- concentrations are equal. Pure water is a common example of a neutral solution, with a pH of 7 at 25°C. pH is calculated using the formula pH=-log[H+], and for neutral solutions, [H+] is 1×10^-7 mol/L, resulting in a pH of 7.

Sodium hydroxide (NaOH) is prepared commercially by the chlor-alkali process. In this method, electricity is passed through a solution of brine (saltwater). During electrolysis, brine breaks down into chlorine gas (Cl2), hydrogen gas (H2), and sodium hydroxide (NaOH). This process takes place in an electrolytic cell and is one of the most important industrial methods for producing sodium hydroxide.

Lemon juice is acidic in nature. It contains citric acid, which gives it a tangy flavor. Tomatoes are also acidic due to their natural acids, but lemon juice is a stronger acid. Oranges, while slightly acidic, are milder than lemons. All of the options listed are acidic in nature.