A solution is obtained by dissolving \(6 \mathrm{~g}\) of urea (mol. wt. \(=60\) ) in a litre solution, another solution is prepared by dissolving \(34.2 \mathrm{~g}\) of cane sugar (mol. wt. = 342 ) in a litre of solution at the same temperature The lowering of vapour pressure in the first solution is: (a) Same as that of second solution (b) Double that of second solution (c) Half that of second solution (d) Nearly one fifth of the second solution

Molarity, often represented by the symbol 'M', is a measure of the concentration of a solution. It is defined as the number of moles of a solute that are present in one liter of the solution. Simply put, molarity tells us how 'strong' or 'concentrated' a solution is.

Calculating molarity is straightforward with the formula: \[ M = \frac{\text{mass of solute (g)}}{\text{molar mass of solute (g/mol)} \times \text{volume of solution (L)}} \].

When students tackle problems involving molarity, it's important to pay attention to units - grams for mass, grams per mole for molar mass, and liters for volume. Consistent units will ensure accurate calculations. In real-world scenarios, chemists and scientists use molarity to determine the exact amount of a substance needed to react or to make a specific concentration of a solution.

Raoult's law is a fundamental principle in physical chemistry that relates to the vapor pressure of solutions. It states that the vapor pressure of a solvent in a solution is directly proportional to the mole fraction of the solvent in the solution. This relationship can be observed with the presence of a non-volatile solute.

The formula for Raoult's law can be expressed as: \[ P = P^\circ_\text{solvent} \times X_\text{solvent} \], where \( P \) is the vapor pressure of the solution, \( P^\circ_\text{solvent} \) is the vapor pressure of the pure solvent, and \( X_\text{solvent} \) is the mole fraction of the solvent.

This law helps us understand how the vapor pressure above a solution changes as more solute is added. For students, this concept underscores the importance of mole fractions and their role in dictating the physical properties of solutions.

Solution concentration refers to the amount of a substance (solute) dissolved in a given volume of solvent to form a solution. There are various ways to express concentration, with molarity being one of the most common. Other measures include molality, mole fraction, and mass percent.

Understanding different concentrations is crucial for correctly interpreting and comparing chemical data. In many chemistry problems, it's essential to convert between these units to solve the problem effectively. For students studying chemistry, grasping the differences between these units and knowing how to convert them is key to mastering the subject.

A non-volatile solute is a substance that has little to no tendency to transform into a gas under existing conditions, meaning it does not vaporize easily. When a non-volatile solute is dissolved into a solvent, it affects the properties of the resulting solution in ways predictable by Raoult's law.

For example, the addition of a non-volatile solute to a solvent decreases the solvent's vapor pressure and can also modify other properties, such as boiling point and freezing point. This is crucial to understand for exercises involving boiling point elevation or freezing point depression. In the context of lowering vapor pressure, the presence of a non-volatile solute reduces the number of solvent molecules that can escape into the vapor phase, leading to a lower vapor pressure than that of the pure solvent.