Class 12 ChemistryImportant Questions for Board Exams

Calculate the packing efficiency of a face-centred cubic unit cell.

What are Frenkel and Schottky defects? In which type of ionic solids does each occur?

What is osmosis? Derive the expression for osmotic pressure. How is it used to determine molecular mass?

18g of glucose (C₆H₁₂O₆) is dissolved in 1kg of water. Calculate the freezing point depression (Kf = 1.86 K kg/mol).

Define conductivity and molar conductivity. How does molar conductivity vary with concentration for strong and weak electrolytes?

What is the difference between order and molecularity of a reaction? Derive the integrated rate equation for a first order reaction.

What is adsorption? Distinguish between physisorption and chemisorption.

What is the Tyndall effect? Give one example.

What is the Ellingham diagram? How is it useful in the extraction of metals?

Describe the froth flotation method for concentration of sulphide ores.

Describe the industrial preparation of sulphuric acid by the Contact process.

Why does fluorine not show positive oxidation state unlike other halogens?

Explain why transition elements show variable oxidation states. Give examples.

What is lanthanoid contraction? What are its consequences?

Write the IUPAC name and draw the structure of [Co(NH₃)₄Cl₂]Cl.

Using VBT, explain the hybridisation and geometry of [Ni(CN)₄]²⁻.

Explain SN1 and SN2 reactions with examples. What factors favour each?

Why is phenol more acidic than ethanol? Explain in terms of structure.

How is ethanol prepared industrially?

Write the mechanism of aldol condensation.

Explain why aldehydes are more reactive than ketones in nucleophilic addition reactions.

Arrange in order of basicity: primary, secondary, tertiary amine (in water). Justify.

How are diazonium salts prepared? Give two uses in synthesis.

What are reducing sugars? Is sucrose a reducing sugar? Why?

Describe the four levels of protein structure.