Acids

Acids are substances that donate hydrogen ions (H⁺) in aqueous solutions.
They have a sour taste, change blue litmus to red, and react with bases to form salt and water (neutralization).
In Bihar, acids are used in agriculture (soil treatment), food processing, and cleaning industries.

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Basic Properties of Acids

• Taste: Sour
• pH: Less than 7
• Litmus Test: Turns blue litmus red
• Conductivity: Good conductor in solution
• Reaction with Metals: Produces hydrogen gas
• Neutralization: Reacts with bases to form salt + water

📝 PYQ (BPSC Teacher): Acid turns which litmus paper red? → Blue
📝 Expected MCQ: What is released when acid reacts with metal? → Hydrogen gas

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Types of Acids

1. Natural/Organic Acids (found in food, plants)

• Citric acid → lemon, orange
• Acetic acid → vinegar
• Lactic acid → curd
• Tartaric acid → tamarind
• Oxalic acid → spinach

2. Mineral/Inorganic Acids (lab/industry)

• Hydrochloric acid (HCl)
• Sulphuric acid (H₂SO₄)
• Nitric acid (HNO₃)
• Carbonic acid (H₂CO₃)

📝 Expected MCQ: Which acid is found in vinegar? → Acetic acid
📝 PYQ (BPSC): Which acid is used in car batteries? → Sulphuric acid

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Strong vs Weak Acids

📝 Expected MCQ: Which of the following is a weak acid? → Acetic acid

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Uses of Acids (Bihar-Based Examples)

🌾 Agriculture

• Acidic fertilizers (e.g., ammonium sulphate) used to treat alkaline soil in parts of South Bihar
• pH testing in Krishi Vigyan Kendras (KVKs) for soil health reports

🍋 Food and Beverage

• Pickle preservation and souring agents use citric, acetic, and tartaric acids
• Common in Mithila and Magahi cuisine

🧪 Industry & Cleaning

• HCl used for cleaning tiles, toilets, and removing rust
• Sulphuric acid used in battery manufacturing and textile industries in Patna and Muzaffarpur

🏥 Medical

• Carbonic acid in aerated drinks
• Boric acid used as mild antiseptic

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Laboratory Safety with Acids

• Always add acid to water, not vice versa
• Use gloves, goggles during experiments
• Store in tightly closed glass bottles
• Neutralize spills with weak base (e.g., baking soda)

📝 Expected MCQ: What is used to neutralize acid spill? → Sodium bicarbonate

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Acid-Base Neutralization

• Acid + Base → Salt + Water
• Example: HCl + NaOH → NaCl + H₂O
• Used in treating acidic soil or alkaline water in Bihar’s agricultural zones

📝 PYQ: What is formed in a neutralization reaction? → Salt and water

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PYQs + Expected MCQs

📝 PYQ (BPSC): Acid used in car batteries? → Sulphuric acid
📝 PYQ: What turns blue litmus red? → Acid
📝 Expected MCQ: Acid found in vinegar? → Acetic acid
📝 Expected MCQ: What is the pH of acid? → Less than 7
📝 Expected MCQ: Which acid is present in tamarind? → Tartaric acid
📝 Expected MCQ: Which acid is used in toilet cleaners? → Hydrochloric acid

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Quick Revision Points

• Acids donate H⁺ ions
• pH < 7, sour taste, blue to red litmus
• Natural acids → in food; Mineral acids → in labs/industry
• Strong acids: HCl, H₂SO₄; Weak acids: CH₃COOH
• Bihar uses: soil treatment, battery, toilet cleaner, pickles
• Neutralization = acid + base → salt + water

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Sources Used

• NCERT Class 7–10 Science
• Lucent GK – Chemistry Section
• Drishti Science Quick Book
• EduTeria + Ghatna Chakra BPSC PYQs
• Bihar Agriculture Department – Soil Reports
• Bihar Industries Dept. – MSME Battery Cluster Data