As we all know that JEE Mains and Advanced happens to be one of the most competitive examinations for admission into premier engineering colleges in India. The list of the engineering colleges in India is long, however, the best of them are the ones sought after by the students. Colleges such as Indian Institute of Technology, Indian Institute of Science, Rajiv Gandhi Petroleum University, Indian Institute of Information Technology, Indian Institute of Science Education and Research etc are always on the radar of the students. Admission into such colleges sets the students on an almost guaranteed path to success, where the top global multinational talent acquisition firms, for their job profiles, hound them. This is one of the most competitive examinations in the world, with a success rate of around 1%.
The chapter of solutions and the chapter of colligative properties is an interesting and an easy chapter that can be covered in a matter of a few hours. Let us first discuss the important topics of the chapter solutions and colligative properties.
- Solutions, constituents, preparation of solution, classification
- Standard units for expressing concentration of different kinds of solutions.
- Henry Law and Raoult’s Law
- Ideal and Non ideal solution, properties, differences, application of Raoult’s Law in Solutions
- Colligative properties of solutions- Elevation of Boiling point, Depression inf freezing points, Lowering of vapour pressure, Osmotic Pressure
- Abnormal colligative properties of various solutions
The above list, more or less, summarizes the important topics that are covered in this chapter. Solutions, as the name suggests, is a liquid mixture of two components, namely, solute and solvents. Let us take the example of brine. Brine is a solution consisting of salt and water. Here, the solute is salt and the solvent is water. Therefore, a solution is created when a solute is dissolved in a solvent which has the affinity for it. For all practical purposes, all solutions are considered to be homogeneous, that means, the solute is uniformly dissolved in the solution. If the solute is non uniformly dissolved, then this is called as heterogeneous solution. Now, a brine solution can be salty, or very salty or extremely salty to taste. But Science does not understand non-quantifiable terms and can only deal with quantifiable terms. Thus, this is where the concept of concentration of solutions comes into the picture. There are various standard units used to describe or express the concentration of the solution. One must have observed on the bottles of cough syrups, cold syrups of terminologies such as “%v/v” or “%w/v” etc. There are numerous methods of expressing concentration such a weight/weight (w/w), weight by volume (w/v), parts per million (ppm), mole fraction etc. Each of these representation of concentration finds it usage in science, and is interchangeable. There are two other forms of concentration called Molarity and Molality, and there is a subtle difference between the two. A colligative property is dependent on the ratio amongst the total quantity of solute units (in the solution) to the total amount of solvent units. It must be borne in mind that colligative properties are not reliant on the chemical nature of the solute or the solvent. Therefore, colligative properties can be related to numerous quantities that are used to express the concentration of a solution, such as molarity, normality, and molality. Common colligative properties include boiling point elevation, depression in freezing point, vapour pressure and osmotic pressure.
Before you begin preparing for the JEE exam, my suggestion will be to go through the chapter of stoichiometry and mole concepts. This will help build the necessary foundation before you dive into this chapter of solutions. Firstly, when you make notes of this subject, I would urge you to read the NCERT book thoroughly. NCERT books are highly under rated but offer the simplest and lucid explanations for every topic. Therefore, before you spend money buying expensive books of foreign authors and others, give the humble NCERT book a chance. It is a joy to read and helps set the foundation for deeper learning.
Next, for the perspective of examination, along with the basic, study the anomalies of colligative properties for different types of solutions. Examiners love this section, as these are abnormal behaviour showcased by solutions. The student must refer to the previous year question papers of both JEE Mains and Advanced.
Numerical problem solving is an extremely necessary task that must be included in the notes of every student. The numerical problems should be varied, of different topics and the solutions must be written down in the notes in a manner that allows for quick revision. Remember, before your actual examinations start, you should have revised the entire content repeatedly. Focus on taking up test series mock examination and take these exams seriously. These exams will help you identify the topics which you are weak at so that you can spend more time dwelling on it and ensuring that all the rough edges have been smoothened.
Solve this question from the chapter: 3g urea is dissolved in 45g of water. The relative lowering of vapour pressure is?