A container holds a sample of hydrogen gas at 300 K. The temperature decreased to 100 K and the pressure remained constant, and the volume changed to 1.0 L. What was the original volume?

Answer : The original volume of gas was, 3.0 L

Explanation :

Charles' Law : It is defined as the volume is directly proportional to the temperature of the gas at constant pressure and number of moles.

or,

where,

are the initial volume and temperature of the gas.

are the final volume and temperature of the gas.

We are given:

Now put all the given values in above equation, we get:

Thus, the original volume of gas was, 3.0 L

first one is the correct answer

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