Gas laws
Charles law

Charles's law states that the volume of a fixed mass of gas is directly proportional to its absolute temperature at constant pressure. This means that as temperature increases, volume increases as well and vice versa.

$$ V \propto T$$ $$ V = kT $$ $$ k = \frac{V}{T} $$ $$ \text{The mathematical expression is}; $$ $$ \frac{V_1}{T_1} = \frac{V_2}{T_2} $$ $$\text{Note: Always covert to kelvin scale} $$ $$ K = (°C + 273) $$
Graphical representation

Calculations

Example 1: The volume of a given mass of a gas is 40cm³ at 27°C. What will be its volume at 90°C. If its pressure remains constant. (NECO)

Solution

$$ V_1 = 40cm³ $$ $$ T_1 = 27°C + 273 = 300K $$ $$ T_2 = 90°C + 273 = 363K $$ $$ V_2 = ? $$ $$ \frac{V_1}{T_1} = \frac{V_2}{T_2} $$ $$ V_2 = \frac{V_1T_2}{T_1} $$ $$ V_2 = \frac{40 × 363}{300} $$ $$ V_2 = 48.4cm³ $$

Example 2: A gas occupies 240cm³ at a temperature of 346K. It's new volume in cm³ at 945K is (NECO)

Solution

$$ V_1 = 240cm³ $$ $$ T_1 = 346K $$ $$ T_2 = 945K $$ $$ V_2 = ? $$ $$ V_2 = \frac{V_1T_2}{T_1} $$ $$ V_2 = \frac{240×945}{346} $$ $$ V_2 = 655.49cm³ $$

Charles law Calculator









Formulas:
  1. For 1: \( T_2 = \frac{V_2T_1}{V_1} \)

  2. For 2: \( V_2 = \frac{V_1T_2}{T_1} \)
Ensure to convert °C to Kelvin before inputting values for temperature

Summary