The molar volume of a gas can be influenced by changes in temperature and pressure, according to the ideal gas law, expressed as:
\[ PV = nRT \]
where:
- \( P \) is the pressure,
- \( V \) is the volume,
- \( n \) is the number of moles of gas,
- \( R \) is the ideal gas constant, and
- \( T \) is the temperature in Kelvin.
An increase in the molar volume (the volume occupied by one mole of gas) by a factor of 2 could be caused by:
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Decreasing Pressure: If the temperature remains constant and the pressure is halved (assuming a constant amount of gas), the volume will double. This is in accordance with Boyle's Law, which states that for a given amount of gas at constant temperature, pressure and volume are inversely related.
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Increasing Temperature: If the pressure remains constant and the temperature is increased, the volume will also increase. According to Charles's Law, the volume of a gas is directly proportional to its absolute temperature when pressure is held constant.
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Increasing the Amount of Gas: If you double the number of moles of gas while keeping the pressure and temperature constant, the molar volume could also appear to double, though this doesn't really change the per-mole volume—it just means there’s more gas occupying the larger total volume.
In summary, a change in either pressure (decreasing it) or temperature (increasing it while holding pressure constant) could account for the increase in molar volume by a factor of 2.
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