Concentration Terms: Molarity, Molality & Formulas
Mastering concentration terms is the first step to conquering Physical Chemistry. This guide categorizes terms based on temperature dependence, a frequent concept in JEE and NEET exams.
1. Temperature Independent Terms (Mass Related)
These terms depend only on mass, which does not change with temperature. They are preferred standards for expressing concentrations in variable temperature environments.
Why Molality is Better?
Since volume expands with heat but mass remains constant, Molality ($m$) and Mole Fraction do not change with temperature, making them more reliable than Molarity.
Figure: Comprehensive Chart of Concentration Definitions and Formulas
2. Temperature Dependent Terms (Volume Related)
These terms involve the volume of the solution. Since liquids expand or contract with temperature, these values fluctuate.
Important Relations
- Normality vs Molarity: $$ N = n \times M $$ (where $n$ is the n-factor or valency factor).
- Dilution Equation: $$ M_1V_1 = M_2V_2 $$ (Moles remain constant before and after dilution).
3. Parts Per Million (ppm)
Used for very dilute solutions, such as measuring pollutants in air or water hardness.
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