NCERT Exemplar Solutions for Class 12 Chemistry Chapter 2: Solutions
The second chapter of Class 12 Chemistry, Solutions, deals with mixtures formed by combining two or more substances. Solutions are an integral part of our daily life as well as industrial processes. Whether it is a salt solution in water, carbonated drinks, or alloys used in construction, the concept of solutions is everywhere. This chapter helps students understand different types of solutions, their properties, concentration terms, and the laws governing their behavior. The NCERT Exemplar Solutions provide detailed explanations of complex questions, making it easier for learners to master this vital topic.
Types of Solutions
Solutions can be classified based on the physical state of solute and solvent. These include solid in solid, solid in liquid, liquid in liquid, gas in liquid, and gas in gas solutions. For example, alloys are solid-solid solutions, while aerated water is an example of gas in liquid. The Exemplar problems encourage students to identify real-life examples of different types of solutions and apply conceptual knowledge to practical situations.
Concentration Terms
One of the most important sections of this chapter is the different ways of expressing the concentration of a solution. Students learn about mole fraction, molarity, molality, and percentage composition. Each unit has its own significance depending on the condition under which the solution is studied. Exemplar questions often require conversions from one concentration term to another. For example, a problem may ask to calculate molality from molarity when density of the solution is given. Such practice strengthens a student’s numerical ability and conceptual clarity.
Solubility
The solubility of solids and gases in liquids forms another key concept. For solids in liquids, factors like temperature and the nature of solute and solvent play an important role. For gases in liquids, Henry’s law states that the solubility of a gas is directly proportional to the pressure of the gas above the solution. This principle has practical applications in the production of carbonated drinks and in understanding how aquatic life adapts to changes in dissolved oxygen. Exemplar solutions provide detailed steps to solve numerical problems on Henry’s law, making it easier for students to understand real-world applications.
Colligative Properties
Perhaps the most significant part of this chapter is colligative properties. These properties depend on the number of solute particles and not on their nature. The four major colligative properties are:
-
Relative lowering of vapor pressure
-
Elevation of boiling point
-
Depression of freezing point
-
Osmotic pressure
Through these properties, one can determine the molar mass of solutes. Exemplar questions require applying formulas and conceptual reasoning to solve problems related to these properties. For example, calculating the molar mass of a solute by measuring the depression in freezing point of its solution is a typical type of Exemplar problem.
Abnormal Molar Masses and Van’t Hoff Factor
Sometimes, observed colligative property values do not match the expected ones. This leads to the concept of Van’t Hoff factor (i), which accounts for association or dissociation of solute particles. Electrolytes like sodium chloride dissociate in water, leading to higher values of colligative properties, while substances like acetic acid may associate in benzene, leading to lower values. The Chemistry Exemplar solutions guide students in applying the Van’t Hoff factor to correct molar mass calculations. This section is particularly important for competitive exams as it tests both conceptual depth and numerical skills.
Importance of NCERT Exemplar Solutions
The NCERT Exemplar Solutions for Chapter 2 provide step-by-step approaches to both numerical and theoretical questions. They also include higher-order reasoning problems that go beyond the textbook, preparing students for board as well as entrance exams. The detailed solutions not only clear doubts but also help in developing logical thinking, making this chapter easier to grasp.Also, solve questions of NCERT with the help of NCERT solutions for class 12 Chemistry.