Solutions

The opening chapter of Class 12 Chemistry — and one of the most reliably scoring chapters for both Boards and competitive exams (typically 4-6 marks in Boards, 1-2 questions in JEE/NEET every year). We build the entire physical chemistry of homogeneous mixtures from the ground up: the nine types of solutions, every way to express concentration (mass %, ppm, mole fraction, molarity $M$, molality $m$, normality), the temperature-dependence of solubility and Henry's law for gases, the vapour-pressure behaviour of liquid-liquid solutions via Raoult's law, the crucial distinction between ideal and non-ideal solutions (positive and negative deviations, azeotropes), and the four colligative properties — relative lowering of vapour pressure, elevation of boiling point ($\Delta T_b = K_b\, m$), depression of freezing point ($\Delta T_f = K_f\, m$), and osmotic pressure ($\Pi = CRT$) — used to determine molar masses. We finish with abnormal molar masses and the van't Hoff factor $i$ that corrects for dissociation and association. By the end you will have mastered every formula, every numerical technique, and every exam trap in the chapter.