Chemistry for the BUET Written Paper
Core areas examined
Expect questions spanning atomic structure and periodicity, chemical bonding and molecular geometry, stoichiometry and the mole, gas laws, equilibrium and Le Chatelier's principle, acid-base and buffer calculations, thermodynamics and thermochemistry, electrochemistry, and introductory organic functional-group chemistry. The written paper favors multi-step numerical work and explanations of trends.
Concepts to master
Be able to predict hybridization and shape using VSEPR and to explain bond polarity versus molecular polarity. Understand how ionization energy, atomic radius, and electron affinity trend across periods and down groups, and why anomalies occur. For equilibrium, write the expression correctly and reason about shifts without confusing rate with extent. For buffers, use the Henderson-Hasselbalch relation. For electrochemistry, keep oxidation at the anode straight.
Common traps
- Confusing the number of moles with molarity in dilution problems.
- Forgetting that solids and pure liquids do not enter equilibrium expressions.
- Treating a strong acid and weak acid identically when computing pH.
- Mixing up oxidation and reduction half-reactions at electrodes.
- Ignoring limiting reagent when two reactant amounts are given.
Worked example
How many grams of NaCl are needed to prepare 500 mL of 0.20 M solution? Moles = 0.20 × 0.500 = 0.100 mol. Molar mass ≈ 58.5 g/mol, so mass = 0.100 × 58.5 ≈ 5.85 g. Rule of thumb: always convert volume to liters before multiplying by molarity, and identify the limiting reagent before computing product yield.
Strategy
Write balanced equations before any calculation, keep significant figures consistent, and label units at every step. For organic questions, identify the functional group first, then reason about reactivity patterns rather than memorizing isolated reactions.