QQuestion
State and explain Charles’s law. Determine the value of absolute zero on the Celsius scale from Charles’s law. [1+2]
✓Answer
Charles’s Law: At constant pressure, the volume of a fixed mass of gas increases or decreases by 1/273 of its volume at 0°C for every 1°C rise or fall in temperature.
If V₀ is the volume of a gas at 0°C, then its volume at t°C is:
Vt = V₀ \left(1+\frac{\text{t}}{273}\right)
or, Vt = \frac{\text{V₀}(273+\text{t})}{273}
Therefore, \frac{\text{Vₜ}}{273+\text{t}}=\frac{\text{V₀}}{273}
Hence, at constant pressure,
\frac{\text{V}}{\text{T}}=\text{Constant}Determination of Absolute Zero
According to Charles’s law,
Vt = V₀ \left(1+\frac{\text{t}}{273}\right)
At absolute zero, the volume of an ideal gas theoretically becomes zero.
Therefore, 0 = V₀ \left(1+\frac{\text{t}}{273}\right)
or, 1 + \frac{\text{t}}{273} = 0
or, t = −273°C
Hence, the value of absolute zero on the Celsius scale is −273°C.
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