Board-style MCQs and short questions in the BIEK / Sindh Board pattern. Tap an option to check yourself instantly. Solved questions are at the bottom.
Multiple-choice questions
Solved short questions & self-assessment (past papers)
Outline the manufacture of urea
Ammonia and carbon dioxide react under pressure: 2NH₃ + CO₂ → NH₂COONH₄ (ammonium carbamate), which then dehydrates to NH₂COONH₄ → CO(NH₂)₂ + H₂O.
Overall: 2NH₃ + CO₂ → urea + water. Urea is ~46 % N — Pakistan's main fertilizer.
Describe the three zones of a cement rotary kiln
Raw meal enters the cool top and slides down to the flame:
1) Pre-heating/drying (~500 °C) — water removed.
2) Calcination (~900 °C) — CaCO₃ → CaO + CO₂.
3) Clinkering (~1450 °C) — CaO + SiO₂/Al₂O₃/Fe₂O₃ → clinker, ground with gypsum to make cement.
Why is cracking necessary in oil refining?
Fractional distillation yields too much heavy oil and not enough petrol. Cracking breaks large molecules into smaller ones, giving more petrol and useful alkenes, e.g.
C₁₂H₂₆ → C₈H₁₈ + 2C₂H₄ → extra petrol + ethene (for plastics).