RT 130 Rey Quiz #3 2.4.1 - 2.5.2

Diffusion is intermolecular mingling that results from gas molecules colliding and pushing each other around until a homogeneous mixture results.

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calculate relative humidity and percent body humidity.. 2.4.2

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saturation

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Gas Diffusion

D gas ~ 1/square root of gmw

Diffusion Coefficient

Diffusion Coefficient: the rate of diffusion of a gas. In cgs units, it is defined as the number of milliliters of a gas at 1 atmosphere of pressure that will diffuse a distance of 1 µ meter over a square centimeter surface area per minute. Lighter gases diffuse rapidly, whereas heavy gases diffuse more slowly. Anything that increases kinetic activity will increase diffusion, such as heating and mechanical agitation

Explain the effect that temperature has on evaporation and humidity 2.4.3

Factors that influence vaporization are: Temperature: increased temperature will increase the rate of vaporization, cooler temperatures will slow down vaporization. Pressure: air pressure above a liquid surface opposes vaporization, so high air pressure means less vaporization. Whereas low air pressure will allow more vaporization from a liquid. Surface area: The greater the available surface area, the greater the rate of liquid evaporation.

Gas Pressure

Gas Pressure All gases exert a pressure no matter where they are; dissolved in blood or contained in a cylinder or free from the atmosphere. The pressure they exert when dissolved in a gas is called tension. Gas tension depends on its kinetic activity. Gravity affects gas pressure by increasing its density. The more dense a gas the more molecular collisions. It is why atmospheric pressure decreases with altitude and at sea level atmospheric pressure equals 760 mmHg. Pressure is a measure of force per unit area. SI N/m2 (newton per meter squared) or Pa (pascal) cgs is dynes/cm2 fps is lb/in2 (pounds per square inch) Pressure can also be measured indirectly as the height of a column of liquid; inches of mercury (in Hg), millimeters of mercury (mmHg), centimeters of water (cm H20).

Atmospheric pressure

Gas Pressure All gases exert a pressure no matter where they are; dissolved in blood or contained in a cylinder or free from the atmosphere. The pressure they exert when dissolved in a gas is called tension. Gas tension depends on its kinetic activity. Gravity affects gas pressure by increasing its density. The more dense a gas the more molecular collisions. It is why atmospheric pressure decreases with altitude and at sea level atmospheric pressure equals 760 mmHg. Pressure is a measure of force per unit area. SI N/m2 (newton per meter squared) or Pa (pascal) cgs is dynes/cm2 fps is lb/in2 (pounds per square inch) Pressure can also be measured indirectly as the height of a column of liquid; inches of mercury (in Hg), millimeters of mercury (mmHg), centimeters of water (cm H20). The height of a column of mercury is not a true measure of pressure. Height is a linear measure, whereas pressure represents force per unit area. However the measurements are still used. An actual water column is not the best to use since it would have to be 33.9 feet (fresh water) for 1 atm or 33 feet for salt water. Pressure = Height x density (Mercury ht: 76 cm or 760 mm or 29.9 inches density: 13.6 g/cm³ or 0.491 lbs/in³) Standards in pressure are: cgs units: 1 atm = 1034g/cm2 fps units: 1 atm = 14.7 lb/in2 One kPa (kilopascal) equals about 10 cm H2O. Thus, a pressure of 10 kPa equals about 100 cm H2O. Conversely, a pressure of 60 cm H2O equals about 6 kPa.

Gaseous Diffusion The process whereby molecules move from areas of high concentration to areas of lower concentration due to kinetic energy.

Gaseous Diffusion The process whereby molecules move from areas of high concentration to areas of lower concentration due to kinetic energy.

Graham's Law

Graham's law is used to quantify gas diffusion rates. The rate of diffusion of a gas (D) is inversely proportional to the square root of its gram molecular weight:

Explain the kinetic energy activity of gases. 2.5.1

Kinetic Activity of Gases The velocity of gas molecules is directly proportional to temperature. Increased temperature means increased kinetic activity, increased collisions, and increased pressures. Cooling has the opposite effect.

explain the concepts of Avogadro's Law, molar volume, density, diffusion of gases (Graham's Law), gas pressure, partial pressure (Dalton's Law), solubility of gases in liquids (Henry's Law) 2.5.2

Molar Volume Avogadro's Law: states that 1 gram atomic weight of any substance contains exactly the same number of atoms, molecules, or ions 6.023 X 1023 In SI units this is one mole. One mole of any substance should occupy the same volume, under the same conditions (constant temperature and pressure). Molar Volume: is the ideal volume for one mole of a gas. A dry gas at a standard temperature of 0º C and atmospheric pressure of 760 mm Hg (STPD) the ideal molar volume of any gas is 22.4 L (with some variations). CO2 is closer to 22.3 L. These values are used to calculate gas densities and convert dissolved gas volumes into moles per liter.

body humidity

Percent Body Humidity (%BH) Percent body humidity (%BH) of a gas is the ratio of its actual water vapor content to the water vapor capacity in saturated gas at body temperature (37o C). Saturated gas (capacity) at body temperature is 43.8 mg/L (44 mg/L) content (absolute humidity) % BH = _________ x 100 capacity at 37 degrees Celsius OR %BH = content (absolut humidity)/43.8 mg/L x 100 Example: saturated air at 20 degrees Celsius contains about 17.3 mg/L water vapor, whereas saturated air at body temperature contains 43.8 mg/L. 17.3/43.8 X 100 = 40%

describe the properties of gases and how they relate to liquids 2.5

Property of gases Exert pressure Capable of flow Exhibit the property of viscosity Readily compressed and expanded Fill the spaces available to them by diffusion

relative humidity

Relative humidity is the ratio of a gases actual water vapor content to its saturated capacity at a given temperature. It is expressed as a percent. GET MORE INFO FROM PREVIOUS QUIZLET WORK

absolute humidity

absolute humidity is the actual amount or weight of water vapor in a gas, unit measure is milligrams of water vapor per liter of gas (mg/L). Saturated air means that it is holding all the water vapor that it hold, its saturated capacity (100% relative humidity). This is temperature dependent. Air saturated with water vapor at 37o C and 1 atm (760 mmHg) has an absolute humidity of 43.8 mg/L. If the air were only 50% saturated, to calculate out the absolute humidity: .50 X 43.8 mg/L = 21.9 mg/L