Final answer:
To find the pressure of a gas collected over water at 30°C with an atmospheric pressure of 758.8 mmHg, subtract the vapor pressure of water at 30°C from the total pressure to get the gas pressure.
Step-by-step explanation:
The question is asking about the pressure of a gas that was collected over water at 30°C when the atmospheric pressure was measured at 758.8 mmHg.
To find the pressure of the gas alone, one must subtract the vapor pressure of water at 30°C from the atmospheric pressure. The vapor pressure of water at 30°C can be found in standard tables and needs to be subtracted from the total pressure to obtain the pressure of the gas.
For example, if the vapor pressure of water at 30°C is say, 31.8 mmHg (this value may vary based on the reference, so the actual value should be looked up), the pressure of the collected gas would be calculated as follows:
Pressure of the gas = Atmospheric pressure - Vapor pressure of water at 30°C
Pressure of the gas = 758.8 mmHg - 31.8 mmHg
Pressure of the gas = 727.0 mmHg
This is the pressure of the gas collected over water after accounting for the vapor pressure of water.
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