What is the partial pressure of hydrogen gas collected over water at standard atmospheric pressure and 25oC if the saturation vapour pressure of water at sa...

What is the partial pressure of hydrogen gas collected over water at standard atmospheric pressure and 25oC if the saturation vapour pressure of water at saturation vapour pressure of water is 23 mm Hg at that temperature?

Answer Details

When a gas is collected over water, some of the water vapor in the air above the liquid will dissolve into the water, causing the total pressure above the liquid to be higher than the pressure of the gas alone. This additional pressure is called the vapor pressure or saturation pressure of the water and depends on the temperature. At standard atmospheric pressure and 25°C, the saturation vapor pressure of water is 23 mmHg. Therefore, if we collect hydrogen gas over water at this temperature and pressure, the total pressure will be the sum of the partial pressure of the hydrogen gas and the vapor pressure of water, which is 23 mmHg. To determine the partial pressure of the hydrogen gas alone, we can use Dalton's law of partial pressures, which states that the total pressure of a mixture of gases is equal to the sum of the partial pressures of the individual gases. In this case, we know that the total pressure is the standard atmospheric pressure, which is approximately 760 mmHg. So, the partial pressure of the hydrogen gas can be calculated as follows: Partial pressure of hydrogen gas = Total pressure - Vapor pressure of water Partial pressure of hydrogen gas = 760 mmHg - 23 mmHg Partial pressure of hydrogen gas = 737 mmHg Therefore, the correct answer is 737 mmHg.