1. Does molarity change if I add more solute without changing the volume?

Yes. Molarity is directly proportional to the number of moles ($n$). If you add solute, $n$ increases while $V$ remains constant, leading to a higher molarity.

2. How do I calculate the molarity of a mixture of two solutions?

Use the formula: $M_{mix} = \frac{M_1V_1 + M_2V_2}{V_1 + V_2}$. This is commonly tested in JEE Advanced for non-reacting solutes.

3. What is the relation between Molarity (M) and Molality (m)?

The relationship is: $m = \frac{1000M}{1000d - M \times M_{solute}}$, where $d$ is density in g/mL. Molality is often preferred because it is temperature-independent.

4. Why is molarity of pure water considered 55.5 M?

Pure water has a density of $1000\text{ g/L}$. Since the molar mass of water is $18.02\text{ g/mol}$, the calculation is $1000 / 18.02 = 55.505\text{ mol/L}$.

5. Can Molarity be used for gases?

Yes, though partial pressure is more common. For an ideal gas, $M = n/V = P/RT$. This links thermodynamics directly to concentration.

6. What happens to molarity during a volume contraction?

If the final volume is less than the sum of individual volumes (common in ethanol-water mixes), the molarity will be higher than the theoretically calculated value.

7. Is molarity the same as Formality?

Formality is used specifically for ionic compounds (like NaCl) where "moles" refers to formula units, but numerically they are usually identical in standard chemistry problems.

8. How does M1V1 = M2V2 handle stoichiometry?

The dilution law assumes moles remain constant ($n_1 = n_2$). If a reaction occurs (like titration), you must use $n_1M_1V_1 = n_2M_2V_2$ where $n$ is the valency factor.

9. What is the difference between "Molar" and "Molar concentration"?

They are the same. "Molar" (M) is the unit, while "Molar concentration" is the property being measured.

10. Can Molarity be zero or negative?

Molarity must be positive. A zero molarity indicates a pure solvent with no solute present.