Gases. Pressure is a force per unit area. For gas, F P= ------- A Force = (mass*acceleration) or F=ma F orce is expressed in Newtons (N) and area is expressed in square meters (m2) The SI unit of pressure is N/m2 is called Pascal (Pa) For liquid P = g ·h ·d
Force = (mass*acceleration) or F=ma
F orce is expressed in Newtons (N) and area is expressed in square meters (m2) The SI unit of pressure is N/m2 is called Pascal (Pa)
P = g ·h ·d
g = gravitational force 9.81 m/s2h = height of a column d = density of a liquid
At sea level, The standard atmospheric pressure is the pressure sufficient to support a column of mercury 760mm in height.
1.0 atm = 760 mmHg = 760 torr = 1.01325 bar = 1.01325x105 Pa
question : what is the height of a column of water that exerts the same pressure as acolumn of mercury 76.00cm high? Density of mercury is 13.6g/ml
a) convert to 0.357 atm to bar.
b) convert 147200 Pa to torr
Pinitial . Vinitial = constant = Pfinal . Vfinal
----------- = ----------
In 1848 William Thomson (Lord Kelvin) proposed an absolute temperature scale known as Kelvin scale. On this scale 0°K is called absolute zero, equals -273.15°C.
T (K) = t ( C) +273.15
the standard temperature for gases is defined as 0 C=273.15K and the standard pressure is defined as 1atm=760mmHg.
These Standard conditions are usually abbreviated as STP.
P = 1 atm = 760 mm Hg
T = 0°C = 273.15 K
At 1.0 atmosphere pressure and 0°C,
1 mole of any gas (i.e. 6.02 x10over23 gas molecules) occupies approximately 22.4 liters volume.
1 mol gas = 22.4 L gas
This equation is known as the ideal-gas equation . An ideal gas is a gas whose physical behavior is accurately described by the ideal-gas equation.
Temperature, T, must always be expressed on an absolute-temperature scale (K)
The quantity of gas, n, is normally expressed in moles
The units chosen for pressure and volume are typically atmospheres (atm) and liters (l),
however, other units may be chosen PV can have the units of energy:
question : what is the mass of propane, C3H8 in a 50.0L container of the gas at STP?
question: calculate the molar mass of a liquid that vaporized at 100°C and 755 Torr yields 185mL of vapor with a mass 0.523g
Dalton’s law The total pressure of a mixture of gases equals the sum of the pressures that each would exert if it were present alone.
Pt is the total pressure of a sample which contains a mixture of gases
P1, P2, P3, etc. are the partial pressures of the gases in the mixture
the term (X1= n1/nt ) is the mole fraction of a substance in the gaseous mixture.
The mole fraction of a component expresses the ratio of the number of moles of one component to the total number of moles in the mixture.
question : A gaseous mixture made from 10 g of oxygen and 15 g of methane is placed in a 10.0 L vessel at 25°C. What is the partial pressure of each gas, and what is the total pressure in the vessel?
question : the main component of dry air by volume N2 78.08%, O2 20.95% Ar 0.93% and CO2 0.04%. what are the partial pressures of each of the four gases in a sample of air at 1.00atm.
question : the total pressure of a gas mixture which containing 0.2 mol of CH4, 0.3 mol of N2 and 0.5 mol of H2, is 2atm. Calculate the partial pressures of each gases in atm.
Al (s) + HCl (aq)→ AlCl3(aq) + H2(g)
if 35.5ml of H2 is collected over water at 26 °C and barometric pressure of 755.0mmHg, how many moles of HCl must have been consumed Pwater= at 26 C is 25.2mmHg
0,37gr KClO3 was heated and O2 produced in this reaction wwas collected over water. The temperatuer of water is 23°C ve atmosferic pressure is 751mmHg. What is the volume of O2 collected over water. Vapor pressure of water at 23°C is 21,1mmHg
The root mean square speed urms
for R must be 8.314 joule mol/K
for M must be in kg
Diffusion is the process of the mixing of gases with one another. Each gas spreads throughout the mixture until its partial pressure is the same everywhere
Effusion is a process in which a gas escapes from its container through a tiny hole.
At a given temperature, the rates of effusion of a gas molecules are inversely proportional to the square roots of their molar masses.
Effusion time and rates are inversely related.
question: if an unknown gas has a effusion rate 0.468 times the rate of O2 at the same temperature, what is the molecular weight of the unknown gas?