Question
A sample of nitrogen gas is collected overwater at a temperature of 23◦C. What is the pressure of the nitrogen gas if the atmospheric pressure is 744 mmHg?
Answer in units of mmHg.
Not sure of formula for this
Answer in units of mmHg.
Not sure of formula for this
Answers
A gas 'collected over water' is a mixture of water vapor and the gas. So
P,total = P,gas + P,water vapor
You'll solve for P,gas and to do that, you'll need data for vapor pressure of water at 23 C.
P,water vapor = 21.1 mm Hg (different sources may show different values)
Substitute:
744 = P,gas + 21.1
P,gas = ?
P,total = P,gas + P,water vapor
You'll solve for P,gas and to do that, you'll need data for vapor pressure of water at 23 C.
P,water vapor = 21.1 mm Hg (different sources may show different values)
Substitute:
744 = P,gas + 21.1
P,gas = ?
I guess I am dumb I don't get it
What don't you get? Dalton's law of partial pressures tells us that the total pressure of a system is the sum of the partial pressures of each gas. You have two gases in this system; i.e., N2 gas and water (as a vapor which is a gas). So according to Dalton's Law, the total pressure, which is given in the problem as 744 mm, is the total of the two pressures.
Ptotal = pH2O + pN2
Ptotal = 744 (from the problem)
pH2O = 21.1 (from a table)
pN2 = ?
Ptotal = pH2O + pN2
Ptotal = 744 (from the problem)
pH2O = 21.1 (from a table)
pN2 = ?