Give Short Answers to the following questions. (Any EIGHT)

Here are the solutions to the questions: SECTION - I Q#2: Give Short Answers to the following questions. (Any EIGHT) 1. Why diamond is a non-conductor while graphite is conductor? In diamond*, each carbon atom is sp^3 hybridized, forming four strong sigma bonds. All valence electrons are localized in these bonds, so there are no free electrons to conduct electricity. In graphite*, each carbon atom is sp^2 hybridized, forming three sigma bonds. The remaining unhybridized p-orbitals overlap to form a delocalized pi electron cloud, providing free electrons for electrical conduction. 2. How is gypsum converted into Plaster of Paris? Gypsum (calcium sulfate dihydrate, CaSO_4 · 2H_2O) is converted into Plaster of Paris (calcium sulfate hemihydrate, CaSO_4 · (1)/(2)H_2O) by heating it to a temperature between 120 ^C and 180 ^C. This process removes three-quarters of its water of crystallization. CaSO_4 · 2H_2O 120-180^ CaSO_4 · (1)/(2)H_2O + (3)/(2)H_2O 3. Why is the aqueous solution of Na_2CO_3 alkaline in nature? Sodium carbonate (Na_2CO_3) is a salt formed from a strong base (NaOH) and a weak acid (H_2CO_3). When dissolved in water, the carbonate ion (CO_3^2-) undergoes hydrolysis, reacting with water to produce hydroxide ions (OH^-), which makes the solution alkaline. CO_3^2- (aq) + H_2O (l) HCO_3^- (aq) + OH^- (aq) 4. What is the chemistry of borax bead test? In the borax bead test*, borax (Na_2B_4O_7 · 10H_2O) is heated to form a transparent glassy bead of sodium metaborate (NaBO_2) and boric anhydride (B_2O_3). When this bead is heated with a colored metal salt, the metal oxide reacts with boric anhydride to form a characteristic colored metal metaborate bead. Na_2B_4O_7 · 10H_2O heat 2NaBO_2 + B_2O_3 + 10H_2O Metal oxide + B_2O_3 heat Metal metaborate (colored bead) 5. How is boric acid dehydrated stepwise when heated strongly? Boric acid (H_3BO_3) dehydrates in a stepwise manner upon strong heating: 1. At about 100 ^C, it loses one molecule of water to form metaboric acid (HBO_2). H_3BO_3 100^ HBO_2 + H_2O 2. At about 140 ^C, metaboric acid polymerizes to form tetraboric acid (H_2B_4O_7). 4HBO_2 140^ H_2B_4O_7 + H_2O 3. Upon strong red heat, tetraboric acid further dehydrates to form boric anhydride (B_2O_3). H_2B_4O_7 red heat 2B_2O_3 + H_2O 6. What is ring test? Give its use. The ring test is a qualitative chemical test used to detect the presence of nitrate ions* (NO_3^-) in a solution. It involves carefully layering a solution of ferrous sulfate (FeSO_4) over concentrated sulfuric acid (H_2SO_4) in a test tube containing the sample. A distinct brown ring forms at the interface of the two layers if nitrate ions are present. 7. Justify that NO acts as an oxidizing agent. Nitric oxide (NO) acts as an oxidizing agent* when it causes another substance to lose electrons (be oxidized) while itself gaining electrons (being reduced). For example, NO can oxidize hydrogen sulfide (H_2S) to sulfur, while NO is reduced from an oxidation state of +2 to 0 (in N_2). 2NO (g) + 2H_2S (g) → N_2 (g) + 2H_2O (l) + 2S (s) 8. Why does aqua regia dissolve platinum? Aqua regia* (a 1:3 mixture of concentrated nitric acid and hydrochloric acid) dissolves platinum because of a synergistic effect. Nitric acid acts as an oxidizing agent, oxidizing platinum to platinum ions (e.g., Pt^2+ or Pt^4+). Hydrochloric acid then reacts with these platinum ions to form stable chloroplatinate complex ions (e.g., [PtCl_4]^2- or [PtCl_6]^2-). The formation of these stable complexes shifts the equilibrium, allowing more platinum to be oxidized and dissolved. 9. What are fertilizers? Why do we need them? Fertilizers* are substances, either natural or synthetic, that are added to soil or applied to plants to supply essential nutrients required for plant growth. We need them because continuous cropping depletes the soil of vital nutrients (like nitrogen, phosphorus, and potassium), and fertilizers replenish these nutrients, ensuring healthy plant development and maximizing agricultural yields. 10. Name essential woody and non woody raw material in the production of paper. Woody raw material*: Wood pulp from trees such as pine, spruce, and eucalyptus. Non-woody raw material*: Agricultural residues like bagasse (from sugarcane), straw (from wheat or rice), cotton linters, and bamboo. 11. Are detergents a threat to aquatic life? Justify. Yes, detergents are a threat to aquatic life. Many detergents contain phosphates, which act as nutrients for algae. This leads to eutrophication*, an excessive growth of algae that consumes dissolved oxygen when they decompose, harming or killing fish and other aquatic organisms. Some detergent components can also be directly toxic to aquatic life. 12. Mention any two conditions which are required for the formation of smog. Two conditions required for the formation of smog are: 1. Presence of primary pollutants such as nitrogen oxides (NOx) and volatile organic compounds (VOCs) from vehicle exhaust and industrial emissions. 2. Sunlight, which provides the energy for photochemical reactions between these pollutants to form secondary pollutants like ozone and peroxyacetyl nitrates (PANs). 3. Stagnant air conditions, often due to temperature inversions, which trap pollutants near the ground. 3 done, 2 left today. You're making progress.