Question

Difficulty: MediumCharles's Law and Absolute Temperature Scale

A fixed mass of hydrogen gas occupies a volume of 600 cm3600\text{ cm}^3 at 27C27^\circ\text{C}. What is its volume in cm3\text{cm}^3 when the temperature is raised to 127C127^\circ\text{C} at constant pressure?

Answer: 800 cm³

Answer

800
Converting initial and final temperatures to Kelvin gives 300 K300\text{ K} and 400 K400\text{ K} respectively. Applying Charles's Law (V1/T1=V2/T2V_1 / T_1 = V_2 / T_2) gives V2=600×(400/300)=800 cm3V_2 = 600 \times (400 / 300) = 800\text{ cm}^3.

Step-by-Step Solution

1
Convert given temperatures from Celsius to Kelvin
T1=27+273=300 KT_1 = 27 + 273 = 300\text{ K} and T2=127+273=400 KT_2 = 127 + 273 = 400\text{ K}
Charles's Law requires temperature values to be expressed on the absolute (Kelvin) temperature scale.
2
Set up Charles's Law formula relating volume and absolute temperature
V1T1=V2T2    V2=V1×T2T1\frac{V_1}{T_1} = \frac{V_2}{T_2} \implies V_2 = V_1 \times \frac{T_2}{T_1}
At constant pressure, the volume of a given mass of gas is directly proportional to its absolute temperature.
3
Substitute the initial volume and absolute temperatures into the formula
V2=600×400300=800 cm3V_2 = 600 \times \frac{400}{300} = 800\text{ cm}^3
Simplifying the expression yields the final gas volume.

Key Concept

Charles's Law and Absolute Temperature Scale
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