Graham’s law states that the rate of diffusion or effusion of a gas is inversely proportional to the square root of its molar mass. 1 M Rate Gas Pressure Pressure is defined as the force applied per unit area: force pressure = area The SI unit of force is the newton (N), where 1 N = 1 kg•m/s 2 The SI unit of pressure is the pascal (Pa), defined as 1 newton per square meter. 1 Pa = 1 N/m 2 Definition and Units of Pressure
CHM2045 Gases 4 Calculation of Pressure A barometer is an instrument that is used to measure atmospheric pressure. Standard atmospheric pressure (1 atm) was originally defined as the pressure that would support a column of mercury exactly 760 mm high. P = hdg h = height in m d = is the density in kg/m 3 g = is the gravitational constant (9.80665 m/s 2 ) Measurement of Pressure A barometer is an instrument that is used to measure atmospheric pressure. 1 atm* = 101,325 Pa = 760 mmHg* = 760 torr* = 1.01325 bar = 14.7 psi * Represents an exact number A manometer is a device used to measure pressures other than atmospheric pressure. 4. Calculate the pressure exerted by a column of mercury 70.0 cm high. Express the pressure in pascals, in atmospheres, and in bars. The density of mercury is 13.5951 g/cm 3 . 5.What pressure (in atm) is exerted by a column of mercury exactly 1 m high? 6.What would be the height of a column of water supported by the pressure you calculated in the problem 4? Assume that the density of the water is 1.00 g/cm3.
7. If a skin diver takes a breath at the surface, filling his lungs with 5.82 L of air, what volume will the air in his lungs occupy when he dives to a depth where the pressure of 1.92 atm? (Assume constant temperature and that the pressure at the surface is exactly 1 atm.) 8. Calculate the volume of a sample of gas at 5.75 atm if it occupies 5.14 L at 2.49 atm. (Assume constant temperature.) 9.At what pressure would a sample of gas occupy 7.86 L if it occupies 3.44 L at 4.11 atm? (Assume constant temperature.)
- Summer '14