When the metal sample reacts with acid, the gas evolved will be collected over water; the gas is said to be "wet". What is the composition of the wet gas? How can the partial pressure of hydrogen be obtained from the total pressure of wet gas? From where will you obtain the necessary data to determine the pressure of hydrogen gas?
Ptotal = pH2 + pH2O
Ptotal is what you read as the room pressure. pH2O is the vapor pressure of H2O which you can obtain from tables in your book at the corresponding temperature.
hgh
The composition of the wet gas collected during the reaction of the metal sample with acid can be determined by calculating the partial pressures of the different gases present.
To obtain the partial pressure of hydrogen gas, you will need to use Dalton's Law of partial pressures. According to this law, the total pressure of a mixture of non-reacting gases is equal to the sum of the partial pressures of each individual gas.
In this case, the total pressure of the wet gas is obtained by collecting it over water. When gases are collected over water, the water vapor also contributes to the total pressure. Since the gas is said to be "wet," it means that water vapor is present in addition to the gas produced by the reaction.
To determine the partial pressure of hydrogen gas, you will need to subtract the vapor pressure of water from the total pressure of the wet gas. The vapor pressure of water depends on the temperature and can be obtained from reference tables or online sources.
By subtracting the vapor pressure of water from the total pressure, you can obtain the partial pressure of hydrogen gas.
To summarize:
1. Collect the gas evolved from the reaction of the metal sample with acid over water.
2. Measure the total pressure of the wet gas.
3. Obtain the vapor pressure of water at the given temperature from reference tables or online sources.
4. Subtract the vapor pressure of water from the total pressure to obtain the partial pressure of hydrogen gas.
Remember, the necessary data such as vapor pressure of water can be found in reference tables or online sources.