a gas is collected over water at 18 degrees celsius at a pressure 755mm. what is the partial pressure of the gas?
Dalton's Law of partial pressure says that the total pressure is the sum of the partial pressures. Therefore,
P total = PH2O + Pgas
755 mm = 18 + ?
solve for ?
To find the partial pressure of the gas, we need to take into account the vapor pressure of water at 18 degrees Celsius. The vapor pressure of water increases with temperature, so we need to refer to a table or use an equation to find the vapor pressure at this temperature.
One commonly used equation to estimate the vapor pressure of water is the Antoine equation:
log(P) = A - (B / (T + C))
In this equation, P is the vapor pressure in mmHg, T is the temperature in degrees Celsius, and A, B, and C are constants specific for water.
Using a reference source, we can find the constants for water: A = 8.07131, B = 1730.63, and C = 233.426.
Substituting the values in the equation, we can solve for the vapor pressure (P) of water at 18 degrees Celsius.
log(P) = 8.07131 - (1730.63 / (18 + 233.426))
By calculating the right side of the equation, we can find the logarithm of P.
log(P) ≈ 8.07131 - (1730.63 / 251.426)
log(P) ≈ 8.07131 - 6.88064
log(P) ≈ 1.19067
To solve for P, we need to find the antilog of 1.19067. By raising 10 to the power of 1.19067, we can find the vapor pressure of water at 18 degrees Celsius.
P ≈ 10^(1.19067)
P ≈ 15.787 mmHg
Now that we know the vapor pressure of water, we can subtract it from the total pressure to find the partial pressure of the gas:
Partial Pressure of Gas = Total Pressure - Vapor Pressure of Water
Partial Pressure of Gas = 755 mmHg - 15.787 mmHg
Partial Pressure of Gas ≈ 739.213 mmHg
Therefore, the partial pressure of the gas is approximately 739.213 mmHg.