A student collects a gas over water in a closed container. The atmospheric pressure is patmos = 1.00 atm, and the vapor pressure of water at the experimental temperature is 0.030 atm. What is the pressure of the dry gas (pgas) in the container?

• A. 1.00 atm
• B. 1.03 atm
• C. 0.030 atm
• D. 0.97 atm

Answer: (D)

Verified step by step guidance

1. Understand that the total pressure inside the container is the sum of the pressure of the dry gas and the vapor pressure of water because the gas is collected over water. This is expressed as: \(P_{\text{total}} = P_{\text{gas}} + P_{\text{water vapor}}\).
2. Identify the given values: atmospheric pressure \(P_{\text{atmos}} = 1.00\) atm, which equals the total pressure \(P_{\text{total}}\), and the vapor pressure of water \(P_{\text{water vapor}} = 0.030\) atm.
3. Rearrange the equation to solve for the pressure of the dry gas: \(P_{\text{gas}} = P_{\text{total}} - P_{\text{water vapor}}\).
4. Substitute the known values into the equation: \(P_{\text{gas}} = 1.00\ \text{atm} - 0.030\ \text{atm}\).
5. Calculate the difference to find the pressure of the dry gas, which represents the pressure exerted by the collected gas excluding water vapor.