Bihar Board Class 10 · Science · Matric exam 2027
Chapter 2: Acids, Bases and Salts — notes
The chapter’s 8 parts in the book’s order — the first idea of each and the points Medha Ma’am writes on the board — and the summary at the end. The full lesson and a check question for each part are in the app.
1. Testing acids and bases with indicators
Okay, so you already know acids taste sour, and bases taste bitter.
- • Acid: sour, blue litmus → red
- • Base: bitter, red litmus → blue
- • Natural indicators: litmus, turmeric
- • Synthetic: methyl orange, phenolphthalein
- • Olfactory indicators: odour changes
- • Curry stain + soap → reddish-brown
2. Acids and bases with metals
Okay, so let's see what happens when an acid meets a metal.
- • Acid + Metal → Salt + Hydrogen gas
- • Zinc + dilute H2SO4 → salt + H2
- • Test: burning candle near gas bubble
- • 2NaOH + Zn → Na2ZnO2 + H2
- • Na2ZnO2 = sodium zincate
3. Carbonates with acids, and neutralisation
Okay, so — all metal carbonates and metal hydrogencarbonates react with acids.
- • Carbonate + Acid → Salt + CO2 + Water
- • Na2CO3 + 2HCl → 2NaCl + H2O + CO2
- • Ca(OH)2 + CO2 → CaCO3 + H2O
- • Base + Acid → Salt + Water
- • NaOH + HCl → NaCl + H2O
4. Metallic and non-metallic oxides
Okay, so let's do a small experiment.
- • Metal oxide + Acid → Salt + Water
- • CuO + HCl → copper(II) chloride, blue-green
- • Metallic oxides = basic oxides
- • Ca(OH)2 + CO2 → CaCO3 + H2O
- • Non-metallic oxides = acidic
5. Ions in water: H+ and OH–
Okay, so let's think about why acids are acids.
- • HCl + H2O → H3O+ + Cl–
- • H+ + H2O → H3O+
- • NaOH(s) → Na+(aq) + OH–(aq)
- • Alkali: a base that dissolves in water
- • H+(aq) + OH–(aq) → H2O(l)
- • Add acid to water, never water to acid
6. The pH scale and strength
Okay, so a universal indicator is a mixture of several indicators.
- • pH scale: 0 (very acidic) to 14
- • pH < 7 acidic, = 7 neutral, > 7 basic
- • More H3O+ → lower pH
- • Body: pH 7.0 to 7.8
- • Acid rain: pH less than 5.6
- • Tooth decay: mouth pH below 5.5
7. Families of salts and their pH
Okay, so let's talk about families of salts.
- • Family: same positive or negative radical
- • NaCl, Na2SO4 → sodium salts
- • NaCl, KCl → chloride salts
- • Strong acid + strong base → pH 7
- • Strong acid + weak base → pH < 7
- • Strong base + weak acid → pH > 7
8. Chemicals from common salt; water of crystallisation
Okay, so common salt is not just for food.
- • 2NaCl + 2H2O → 2NaOH + Cl2 + H2
- • Ca(OH)2 + Cl2 → CaOCl2 + H2O
- • 2NaHCO3 → Na2CO3 + H2O + CO2 (heat)
- • Washing soda: Na2CO3.10H2O
- • Copper sulphate: CuSO4.5H2O (blue)
- • Gypsum CaSO4.2H2O → Plaster of Paris
Summary
Okay, so let's go back over what we covered today. We saw that indicators like litmus, turmeric, methyl orange and phenolphthalein tell us whether something is an acid or a base. Olfactory indicators are a bit different — they change their smell, not their colour. Then we looked at how acids react with metals. That gives a salt and hydrogen gas. Acids also react with metal carbonates and hydrogencarbonates, and that gives a salt, carbon dioxide and water. Remember neutralisation? An acid and a base react together to form a salt and water. We also said metallic oxides are basic, and non-metallic oxides are acidic. Here's an important point — acids give H+(aq) ions, and bases give OH–(aq) ions, but only when they're in water. And the pH scale, from 0 to 14, tells us how acidic or how basic a solution is. 7 sits right in the middle — that's neutral. Towards the end, we met some families of salts and their pH, a few chemicals made from common salt, and water of crystallisation — in copper sulphate, washing soda, gypsum and Plaster of Paris. That's a lot of ground covered today. Which of these felt the trickiest to you?
AskMedha · Medha Ma’am — Bihar Board Class 10 Science, Chapter 2. Written from the textbook, checked twice.
Questions parents and students ask
- How do I get the "Acids, Bases and Salts" notes as a PDF?
- Press "Save as PDF" — the phone’s print sheet opens; choose "Save as PDF" there. The PDF holds the notes only.
- Where are these notes written from?
- From the chapter’s own textbook text, part by part, in the book’s own terms; a second, independent model then checked every part against the book. The full lesson, a check question for each part and the practice are in the AskMedha app.
The same preparation, with Medha Ma’am — on your phone
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