Final answer:
To find the pressure of hydrogen gas collected over water, subtract the vapor pressure of water at 25°C from the ambient pressure. Assuming a vapor pressure of water of 23.8 mm Hg, the pressure of hydrogen would be 686.2 mm Hg.
Step-by-step explanation:
To calculate the pressure of hydrogen gas collected over water using Dalton's Law of Partial Pressures, we first need to consider both the ambient pressure and the vapor pressure of water at the given temperature. Dalton's Law states that the total pressure of a gas mixture is equal to the sum of the partial pressures of each individual gas. For gases collected over water, the total pressure equals the partial pressure of the gas plus the vapor pressure of water.
At 25°C, we would have to look at a reference table to find the vapor pressure of water. Let's assume, for example purposes, that the vapor pressure of water at 25°C is 23.8 torr (or mm Hg since 1 torr = 1 mm Hg). If the ambient pressure is 710 mm Hg, according to Dalton's Law:
Ptotal = Pgas + PH₂O
Therefore, we can rearrange to solve for the hydrogen gas pressure:
Pgas = Ptotal - PH₂O
Pgas = 710 mm Hg - 23.8 mm Hg
Pgas = 686.2 mm Hg
So, the partial pressure of the hydrogen gas collected over water at 25°C with an ambient pressure of 710 mm Hg is 686.2 mm Hg.