\(3.65 \mathrm{~g}\) of \(\mathrm{HCl}\) is dissolved in \(16.2 \mathrm{~g}\) of water The mole fraction of \(\mathrm{HCl}\) in the resulting solution is: (a) \(0.4\) (b) \(0.3\) (c) \(0.2\) (d) \(0.1\)

Mole calculation is an essential concept in chemistry that helps us quantify the amount of a substance. It is especially important for solutions, as it allows chemists to determine the precise number of atoms, ions, or molecules in a given mass of a compound.

Let's simplify the concept like this: imagine a mole as a counting unit, much like a dozen, but instead, it's Avogadro's number, which is approximately 6.022 x 10²³. This immense number helps us to group particles into a manageable set to work with in chemical calculations.

To calculate the number of moles, the formula is quite straightforward:
\[ \text{{number of moles}} = \frac{{\text{{mass of the substance (g)}}}}{{\text{{molar mass of the substance (g/mol)}}}} \].

By understanding and applying mole calculations, students studying for NEET and other competitive exams can tackle problems involving reactions and solution concentrations with confidence.

Molar mass is the mass of one mole of a substance, typically expressed in units of grams per mole (g/mol). It is a fundamental concept, as it bridges the gap between microscopic particles and macroscopic amounts of a substance.

To find the molar mass, one can simply refer to the periodic table. Each element's atomic weight, listed under its symbol, represents the molar mass of that element in grams per mole. For compounds like HCl or H₂O, one must add up the molar masses of all the constituent atoms.

A practical example would be:
\[ \text{{Molar mass of HCl}} = 1 \text{{(Hydrogen)}} + 35.45 \text{{(Chlorine)}} = 36.45 \text{{g/mol}} \].

Understanding molar mass is crucial for accurately measuring chemical quantities, necessary for precision in experiments and in solving problems in chemistry exams like NEET.

Solution concentration refers to the amount of solute that is dissolved in a solvent. One of the ways to express concentration is through mole fraction, which is the ratio of the moles of a particular component to the total moles of all components in the solution.

The formula for mole fraction is quite simple:
\[ \text{{mole fraction}} = \frac{{\text{{moles of the component}}}}{{\text{{total moles in the solution}}}} \].

This dimensionless quantity is a clear indicator of the component's relative proportion in a mixture, and it is particularly useful for calculations involving vapor pressure, boiling point elevation, and freezing point depression. For students prepping for the chemistry portion of NEET, mastering mole fractions is crucial for a thorough understanding of solution properties.

Chemistry for NEET, or the National Eligibility cum Entrance Test, demands a strong grasp of fundamental concepts including mole calculation, molar mass, and solution concentrations. Success in NEET chemistry hinges on a student's ability to apply these concepts to solve complex problems efficiently.

An effective approach to excel in NEET chemistry includes:

• Understanding basic principles and formulas.
• Practicing diverse types of problems.
• Developing quick and accurate calculation skills.
• Recognizing patterns and connections between different topics.

Key to conquering NEET chemistry is not merely memorizing formulas but understanding the underlying principles - allowing for flexible, dynamic problem-solving on exam day.