General Chemistry

The major ingredient of leather is collagen (option B). Leather is produced from animal hides through tanning, and the primary structural protein in animal connective tissue is collagen, which gives leather its strength and durability. Carbohydrates, polymers, and nucleic acids are not the primary components of leather.

Glass is primarily made from sand (silica) and silicates (option C). The main ingredient in glass production is silicon dioxide (SiO2) found in sand, combined with various silicate compounds. Option A is incorrect because quartz is a form of silica itself, not combined with mica. Option B is incorrect because salt is not a standard glass ingredient.

Epoxy resins are primarily used as adhesives (option D). Epoxy resins form strong bonds when cured and are widely used in construction, automotive, and marine applications as structural adhesives. They are not typically used as moth repellants, insecticides, or detergents.

A mixture of water and alcohol can be separated by distillation (option C). Distillation works because water and alcohol have different boiling points (100°C for water, 78°C for ethanol), allowing the alcohol to vaporize first. Filtration separates solids from liquids, evaporation leaves solids behind, and decantation separates immiscible liquids of different densities.

A substance which changes readily into vapour without heating is called volatile (option C). Volatile substances have high vapor pressure at room temperature and evaporate easily. Efflorescent substances lose water of crystallization, effervescent substances release gas bubbles, and synthetic refers to artificially made materials.

Cooking oil can be converted into vegetable ghee by the process of hydrogenation (option B). Hydrogenation adds hydrogen atoms to unsaturated fatty acids in liquid oils, making them solid at room temperature. This is the same process used to make margarine. Oxidation would degrade the oil, distillation separates components, and crystallization is a purification technique.

Combustion produces both heat and light (option C). Combustion is an exothermic chemical reaction between a fuel and oxidant that releases energy in the form of heat and often light (as in flames). Options A and B are incomplete as combustion typically produces both, and option D is incorrect because heat and light are indeed produced.

Photosynthesis is an endothermic process (option B). Photosynthesis absorbs energy from sunlight to convert carbon dioxide and water into glucose and oxygen. Endothermic processes require energy input, whereas exothermic processes release energy. 'Neutral process' and 'thermostatic process' are not standard thermodynamic classifications.

Camphor (option C) exhibits the property of sublimation - it transitions directly from solid to vapour without passing through the liquid phase. Ice melts to water before evaporating, wax melts to liquid, and ethyl alcohol evaporates from liquid. Sublimation is characteristic of certain solids like camphor, dry ice (solid CO2), and naphthalene.

Vanadium Pentoxide (V2O5) is used as a catalyst in the Contact process (option A). The Contact process produces sulfuric acid by oxidizing sulfur dioxide to sulfur trioxide, with V2O5 as the catalyst. The Haber process produces ammonia using iron catalysts, and the Solvay process produces sodium carbonate without V2O5.

Reaction of alcohol with carboxylic acid is known as esterification (option C). Esterification produces an ester and water, catalyzed by acid. This is how fragrances, flavors, and many industrially important compounds are made. Substitution replaces one group, addition adds to a double bond, and hydrogenation adds hydrogen.

Iron filings are magnetic and can be attracted by a magnet while sand is non-magnetic. This property difference allows magnetic separation to effectively isolate the iron from the sand mixture.

The reaction of water with calcium carbide produces acetylene gas and calcium hydroxide. This is a standard laboratory preparation method for acetylene.

Lead nitrate decomposes on heating (thermal decomposition) to form lead oxide, nitrogen dioxide, and oxygen. This is a chemical change as new substances are formed. Sodium chloride and silica are stable to heat, while platinum wire only undergoes physical change.

Copper reacts with dilute nitric acid to form nitrogen monoxide (NO), copper nitrate, and water. The NO is initially colorless but quickly oxidizes in air to brown NO2. With concentrated nitric acid, NO2 is produced directly.

A more reactive metal can displace a less reactive metal from its salt solution. Magnesium is more reactive than zinc (higher in reactivity series), so it can displace zinc from zinc sulphate solution. Lead, iron, and mercury are less reactive than zinc.

PVC (polyvinyl chloride) is produced by polymerization of vinyl chloride monomer (chloroethene). The polymer consists of repeating -CH2-CHCl- units. This is an addition polymerization reaction.

Pure water undergoes self-ionization: H2O ⇌ H+ + OH-. At 25°C, the concentrations of H+ and OH- are equal (10^-7 M each), resulting in neutral pH. This balanced dissociation makes water neither acidic nor alkaline.

Water gas (CO + H2 mixture) is produced by passing steam over white-hot coke (carbon) at about 1000°C. The endothermic reaction is: C + H2O → CO + H2. This is an important industrial gas mixture.

Photosynthesis converts light energy (sunlight) into chemical energy stored in glucose molecules. This occurs in chloroplasts containing chlorophyll, which captures light energy to drive the synthesis of organic compounds from CO2 and water.

Active metals like zinc can displace hydrogen from dilute acids because they are more reactive than hydrogen. Zinc reacts with dilute HCl or H2SO4 to form Zn2+ ions and hydrogen gas. Gold, copper, and silver are less reactive than hydrogen.

Polythene (polyethylene) is produced by polymerization of ethylene (ethene) monomers. The polymer consists of long chains of -CH2-CH2- units formed by addition polymerization. This is one of the most widely used plastics globally.

Sodium thiosulphate (Na2S2O3) is used as a fixer in photography because it dissolves unexposed silver halide crystals from the developed emulsion, making the image permanent and light-fast. Borax is used as a buffering agent, sodium sulphate is a drying agent, and ammonium persulphate is an oxidizer.

The rate of a chemical reaction does not depend on pressure.