Tip 1: How to calculate the gas pressure

To address some physical problems it is necessary to calculate the pressure gas .Therefore, the problem can be referred to as the ambient air and vapor of the substance and a gas which is in the vessel.Exactly how to calculate the pressure gas , depending on what parameters are given in the task.
you need
  • - the formula for calculating the gas pressure.
Guide
1
Find pressure perfect gas in the presence of the average speed of the molecules, the mass of a single molecule, and the concentration of a compound of formula P = ⅓nm0v2, where n - concentration (in grams or moles onliter), m0 - mass of a single molecule.
2
If the condition given the density of the gas and the average speed of its molecules, calculate pressure formula P = ⅓ρv2, where ρ - the density in kg / m3.
3
Calculate pressure , if you know the temperature gas and its concentration, using the formula P = nkT, where k - Boltzmann constant (k = 1,38 · 10-23 mol K1) T - the absolute temperature in K
elvin.
4
Find pressure two equivalent variants of the equation Mendeleev-Clapeyron depending on the known values: P = mRT / MV or P = νRT / V, where R - universal gas constant (R = 8,31 J / mol · K), ν - amount of substance in moles, V - volume gas in m3.
5
If in the problem shows the average kinetic energy of molecules gas and its concentration, get pressure using the formula P = ⅔nEk where Ek - kinetic energy in J.
6
Find pressure of gas laws - isochoric (V = const) and isothermal (T = const), if given pressure in one of the states.At isochoric process pressure ratio in the two states is the ratio of heat: P1 / P2 = T1 / T2.In the second case, if the temperature remains constant, the product of gas pressure its volume in the first state is equal to the same product in the second state: V1 = P1 · P2 · V2.Express unknown quantity.
7
Calculate pressure from the formula of the internal energy of an ideal monatomic gas : U = 3 · P · V / 2, where U - internal energy in J. Hence pressure will be: P =⅔ · U / V.
8
When calculating the partial pressure of steam in the air, if the condition given temperature and relative humidity, express pressure from the formula φ / 100 = P1 / P2, where φ / 100 - RH, P1- partial steam pressure P2 - the maximum value of the water vapor at a given temperature.In use the table during calculation of the maximum vapor pressure (maximum partial pressure), temperature in degrees Celsius.

Tip 2: How to calculate the pressure

even attach a little effort, you can create considerable pressure .All that is needed - is to concentrate effort on a small area.Conversely, if spread evenly over a large area of ​​considerable effort, pressure get relatively small.To find out how it will have to calculate.
How to calculate the pressure
Guide
1
Turn all raw data in SI units: force - in Newton, Mass - in kilograms, area - in square footage, etc.Then after calculating pressure is expressed in Pascal.
2
In case if the problem shows no force and weight of the load, calculate the force of the following formula: F = mg, where F - force (N), m - weight (kg), g - accelerationfree fall equal to 9.80665 m / s².
3
If the conditions of the area, instead of the geometric parameters of the field indicated, which is pressure , first calculate the area of ​​this region.For example, for a rectangle: S = ab, where S - area (m²), a - length (m), b - width (m) .For range: S = πR², where S - area (sqm), π - number "pi "3.1415926535 (dimensionless), R - radius (m).
4
To learn pressure , divide the force by the area: P = F / S, where P - pressure (Pa), F - the force (N), S - area (m²).
5
If necessary, turn the pressure in derived units: kilopascals (1 kPa = 1000 Pa) or megapaskali (1 MPa = 1000000 Pa).
6
To convert the pressure of the atmosphere or Pascal millimeters of mercury use the following relationships: 1 atm = 101325 Pa = 760 mmHg.Art.
7
In preparation accompanying the goods intended for export, it may be necessary to express pressure in pounds per square inch (PSI - pounds per square inch).In this case, refer to the following ratio: 1 PSI = 6894,75729 Pa.
Sources:
  • how to calculate the atmospheric pressure
Helpful Hint
Use aneroid or mercury barometer for precise values ​​if you need to calculate the pressure of the gasduring the experiment or the lab.To measure the pressure in the vessel or gas cylinder, use a conventional or an electronic manometer.
Sources:
  • pressure and density of saturated water vapor depending on the temperature - table
  • formula gas pressure

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