Question

A sample of oxygen gas is collected over water at 25 degrees Celsius and 760 mmHg pressure. What is the pressure of the dry gas alone? The vapor pressure of water at 25 degrees Celsius is equal to 23.8 mmHg.

Options:
a. 736.2 mmHg
b. 736 mmHg
c. 760 mmHg
d. 783.8 mmHg

Answer 1

The pressure of the dry oxygen gas collected over water at 25 degrees Celsius and 760 mmHg is 736.2 mmHg, obtained by subtracting the vapor pressure of water from the total pressure.

Step-by-step explanation:

To find the pressure of the dry gas alone, we need to subtract the vapor pressure of water from the total pressure measured. The total pressure given is 760 mmHg, and the vapor pressure of water at 25 degrees Celsius is 23.8 mmHg. Therefore, the pressure of the dry oxygen gas (O2) is calculated as follows:

Pdry gas = Ptotal - Pwater vapor
Pdry gas = 760 mmHg - 23.8 mmHg
Pdry gas = 736.2 mmHg

So, the correct answer is 736.2 mmHg, which corresponds to option a.