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The questions your board exam loves to ask
800 most-asked Class 11 & 12 (+1 / +2) questions across Physics, Chemistry, Maths and Biology — each with a model answer and the exact marking-scheme points examiners reward. Revise smart, walk in calm.
ChemistryClass 112 markseasy
Equilibrium
Define an acid and a base according to the Bronsted-Lowry concept. What is a conjugate acid-base pair?
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According to the Bronsted-Lowry concept, an acid is a substance that donates a proton (H+) and a base is a substance that accepts a proton. A conjugate acid-base pair is a pair of species that differ by a single proton; for example, in HCl + H2O -> H3O+ + Cl-, HCl/Cl- and H2O/H3O+ are conjugate acid-base pairs.
acid <=> base + H+
Marking-scheme points
- ✓Bronsted acid = proton donor; base = proton acceptor
- ✓Conjugate pair differs by one proton (H+)
- ✓Example: HCl/Cl- and H2O/H3O+
ChemistryClass 112 markseasy
Equilibrium
Calculate the pH of a 0.001 M HCl solution.
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HCl is a strong acid and dissociates completely, so [H+] = 0.001 M = 1 x 10^-3 M. pH = -log[H+] = -log(10^-3) = 3. The solution is acidic (pH < 7).
pH = -log[H+]
Marking-scheme points
- ✓Strong acid: [H+] = 10^-3 M
- ✓pH = -log[H+]
- ✓pH = 3 (acidic)
ChemistryClass 113 marksmedium
Equilibrium
Calculate the pH of a 0.01 M NaOH solution at 298 K.
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NaOH is a strong base and dissociates completely, so [OH-] = 0.01 M = 10^-2 M. pOH = -log[OH-] = -log(10^-2) = 2. Since pH + pOH = 14, pH = 14 - 2 = 12. The solution is basic (pH > 7).
pH + pOH = 14
Marking-scheme points
- ✓Strong base: [OH-] = 10^-2 M -> pOH = 2
- ✓pH + pOH = 14 at 298 K
- ✓pH = 14 - 2 = 12 (basic)
ChemistryClass 112 marksmedium
Equilibrium
What is the ionic product of water (Kw)? State its value at 298 K and its relation with pH.
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Equilibrium
What is a buffer solution? Give one example of an acidic buffer and write the Henderson-Hasselbalch equation.
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Equilibrium
The solubility product (Ksp) of AgCl is 1.8 x 10^-10 at 298 K. Calculate its solubility in mol/L.
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Equilibrium
What is the common ion effect? Explain with a suitable example.
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Redox Reactions
Define oxidation and reduction in terms of electron transfer and oxidation number.
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Redox Reactions
Calculate the oxidation number of manganese in KMnO4 and of chromium in K2Cr2O7.
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Redox Reactions
Balance the following redox reaction in acidic medium by the ion-electron (half-reaction) method: MnO4- + Fe2+ -> Mn2+ + Fe3+.
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Redox Reactions
Define an oxidising agent and a reducing agent with one example each.
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Redox Reactions
What is a disproportionation reaction? Give one example.
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Redox Reactions
In the reaction Zn + CuSO4 -> ZnSO4 + Cu, identify the species oxidised, the species reduced, the oxidising agent and the reducing agent.
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Hydrogen
Why is the position of hydrogen anomalous in the periodic table?
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Hydrogen
What is hard water? Distinguish between temporary and permanent hardness and give one method to remove each.
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Hydrogen
Explain why hydrogen peroxide (H2O2) can act both as an oxidising agent and as a reducing agent.
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The s-Block Elements
Why are alkali metals strong reducing agents?
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The s-Block Elements
What is a diagonal relationship? Why do lithium and magnesium show similar properties?
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The s-Block Elements
Why does lithium show anomalous behaviour compared with the other alkali metals?
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The s-Block Elements
Describe the trend in solubility of the hydroxides and sulphates of alkaline earth metals down the group. Give the flame colours of Ca, Sr and Ba.
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