Acids Bases and Salts — BSSC Chemistry

• Key Fact Oxalic acid (C₂H₂O₄) is found in leafy greens like spinach, tomatoes, and beetroot. • Supporting Detail It is also used in removing rust stains and as a bleaching agent. • Related Concept Other organic acids include citric in lemons and acetic in vinegar. • Why wrong options are wrong Acetic is in vinegar, citric in citrus fruits, lactic in milk. • Exam Trick Remember 'OT' - Oxalic Tomato. • Additional Info Formic acid is found in ant stings and fruits.

• Key Fact The word "acid" originates from the Latin word 'acidus', meaning sour. • Supporting Detail Acids are generally sour in taste and corrosive in nature. • Related Concept They release hydrogen ions (H⁺) in aqueous solutions. • Why wrong options are wrong 'Alumen' is the root for aluminium, not acid. • Exam Trick Acid = Acidus = Sour. • Additional Info Bases are bitter in taste, unlike sour acids.

• Key Fact In distilled water (neutral), litmus has a purple colour. • Supporting Detail Litmus is extracted from lichens, a plant of the Thallophyta division. • Related Concept It turns red in acidic solutions and blue in basic solutions. • Why wrong options are wrong Red and blue are its colours in active acidic/basic media, not neutral. • Exam Trick Neutral = Purple (mixing red and blue gives purple). • Additional Info Universal indicator turns green in neutral solutions, but litmus is purple.

• Key Fact Lewis Theory defines an acid as an electron pair acceptor (e.g., BF₃, AlCl₃). • Supporting Detail A Lewis base is an electron pair donor (e.g., NH₃). • Related Concept Arrhenius focuses on H⁺ / OH⁻ ions in water. • Why wrong options are wrong Bronsted-Lowry defines acids as proton (H⁺) donors, not electron acceptors. • Exam Trick Trick: 'Lewis' starts with L, focus on 'eL'ectrons. • Additional Info Bronsted-Lowry involves proton transfer, resulting in conjugate acids/bases.

• Key Fact Alkalis are a specific type of base that completely dissolve in water (e.g., NaOH, KOH). • Supporting Detail Because they dissolve, all alkalis are bases. • Related Concept However, some bases are insoluble in water (e.g., Cu(OH)₂), meaning not all bases are alkalis. • Why wrong options are wrong Statement 2 is entirely incorrect. • Exam Trick Formula to remember: Alkalis ⊂ Bases (Alkalis are a subset of bases). • Additional Info Examples of insoluble bases: Fe(OH)₃, Cu(OH)₂.

• Key Fact Formic acid (HCOOH) is the most acidic among simple carboxylic acids as it has no alkyl group. • Supporting Detail Alkyl groups like ethyl (C₂H₅) exert an electron-donating inductive effect (+I effect). • Related Concept This effect pushes electrons toward the carboxyl group, making the release of the H⁺ ion less favorable. • Why wrong options are wrong Thus, longer chains mean weaker acids. • Exam Trick Larger Alkyl group = Stronger +I effect = Weaker Acid. • Additional Info This principle applies to all organic acids in determining their strength.

• Key Fact Active metals react with acids to displace hydrogen, forming a salt and releasing Hydrogen (H₂) gas. • Supporting Detail Example: Zn + 2HCl → ZnCl₂ + H₂↑. • Related Concept Only active metals (above hydrogen in the reactivity series) can do this. • Why wrong options are wrong CO₂ is released when acids react with metal carbonates, not pure metals. • Exam Trick Metal + Acid = H₂ pop sound test. • Additional Info Bases also react with certain metals (like Zn, Al) to release H₂ gas.

• Key Fact Thyme leaves are herbs used for culinary and medicinal purposes, not as pH indicators. • Supporting Detail Petunia, Geranium, Hydrangea, and Red Cabbage contain a pigment called Anthocyanin, making them natural indicators. • Related Concept Turmeric is also a natural indicator (turns red in base). • Why wrong options are wrong The question asks for the odd one out; Thyme lacks indicator pigments. • Exam Trick Remember 'TRPHG' - Turmeric, Red cabbage, Petunia, Hydrangea, Geranium as natural indicators. • Additional Info Olfactory indicators change odour, while these change colour.

• Key Fact Tooth decay begins when the pH of the mouth is lower than 5.5. • Supporting Detail Bacteria in the mouth produce acids by degrading sugar and food particles. • Related Concept Tooth enamel, made of calcium phosphate, gets corroded in an acidic environment below 5.5. • Why wrong options are wrong 7.0 is neutral, and 1.5 is the pH of gastric juice in the stomach. • Exam Trick Use basic toothpastes (pH ~9) to neutralize this acid and prevent decay. • Additional Info Acid rain is defined when rainwater pH is below 5.6.

• Key Fact Phenolphthalein is a synthetic indicator that remains colorless in acidic solutions. • Supporting Detail Phenolphthalein turns pink in basic (alkaline) solutions. • Related Concept Methyl Orange turns red in acidic solutions. • Why wrong options are wrong Methyl Orange turns yellow in basic solutions. • Exam Trick Trick: 'MY' (Methyl Yellow in base), 'MR' (Methyl Red in acid). • Additional Info Litmus turns red in acid and blue in base.