Pascal atmospheric pressure

Pump manufacturers express vacuum in aspirated feet of water in a ver r -i (0 psia = -33.9 feet of water). The pharmaceutical and chemical indue r Pascals (100,000 Pascals = atmospheric pressure) and the term TO C. conglomeration of values and conversion n, causes confusion. In ( ... 

Atmospheric Tanks The term atmospheric tank as used here applies to any tank that is designed to be used within plus or minus several hundred pascals (a few pounds per square foot) of atmospheric pressure. It may be either open to the atmosphere or enclosed. Minimum cost is usually obtained with a vertical cylindrical shape and a relatively flat bottom at ground level. 

Pressure Tanks Vertical cylindrical tanks constructed with domed or coned roofs, which operate at pressures above several hundred pascals (a few pounds per square foot) but which are still relatively close to atmospheric pressure, can be built according to API Standard 650. The pressure force acting against the roof is transmitted to the shell, which may have sufficient weight to resist it. If not, the uplift will act on the tank bottom. The strength of the bottom, however, is limited, and if it is not sufficient, an anchor ring or a heavy... 

FIG. 14-53 Pressure for metal Intalox saddles, sizes No, 25 (nominal 25 mm) and No, 50 (nominal 50 mm). Air-water system at atmospheric pressure, 760-mm (30-in) column, hed height, 3,05 m (10 ft), L = liquid rate, kg/(s-m ). To convert kilograms per second-square meter to pounds per hour-square foot, multiply hy 151,7 to convert pascals per meter to inches of water per foot, multiply hy 0,1225, (Coutiesy Notion Company, Akron, Ohio.)... 

Sound pressure The average variation in atmospheric pressure caused by a sound, given in pascals. 

It is conventional to take as the activation volume the value of AV when P = 0, namely —bRT. (This is essentially equal to the value at atmospheric pressure.) Pressure has usually been measured in kilobars (kbar), or 10 dyn cm 1 kbar = 986.92 atm. The currently preferred unit is the pascal (Pa), which is 1 N m 1 kbar = 0.1 GPa. Measurements of AV usually require pressures in the range 0-10 kbar. The units of AV are cubic centimeters per mole most AV values are in the range —30 to +30 cm moP, and the typical uncertainty is 1 cm moP. Rate constant measurements should be in pressure-independent units (mole fraction or molality), not molarity. ... 

So far, we have explained the effects of atmospheric pressure on liquids and how external forces are distributed through liquids. Let us now focus our attention on forces generated by the weight of liquids themselves. To do this, we must first discuss density, specific gravity and Pascal s law. 

The height of the mercury in the system-side column of an open-tube mercury manometer was 10. mm above that of the open side when the atmospheric pressure corresponded to 756 mm of mercury and the temperature was 15°C. What is the pressure inside the apparatus in millimeters of mercury and in pascals ... 

Although the SI unit of pressure is the pascal (Pa), there are several other units in common use. Normal atmospheric pressure is close to 100 kPa, and it is useful to... 

Self-Test 4.3B The atmospheric pressure in Denver, Colorado, on a certain day was 630. Torr. Express this pressure in pascals. 

The accepted SI unit for pressure is the pascal (Pa). Pressure is defined as force per unit area, P/, so the pascai can be expressed by combining the SI units for these two variabies. The SI unit of force is the newton (N), and area is measured in square meters (m ). Thus, the pascai is 1 N/m. Expressed in pascais, the numericai vaiue of atmospheric pressure is quite iarge. By intemationai agreement, 1 atm is defined exactiy in terms of pascais ... 

Column inlet pressures in hplc can be as much as 200 times atmospheric pressure, and hplc columns are packed using much larger pressures (up to 700 times atmospheric). The SI unit of pressure is the Pascal (1 Pa = 1 Nm-2) normal atmospheric pressure is about 105 Pa. Because it is convenient to express pressure using reasonably small numbers, experimental workers and instrument manufacturers report pressures in bar, or pounds per square inch (psi), or sometimes in kg cm-2. The bar is defined by 1 bar = 105 Pa, so that 1 bar corresponds roughly to normal atmospheric pressure. You will need to be able to convert between these units. 

Before we start describing the gas law relationships, we will need to describe the concept of pressure. When we use the word pressure with respect to gases, we may be referring to the pressure of a gas inside a container or we might be referring to atmospheric pressure, the pressure due to the weight of the atmosphere above us. The pressure at sea level is 1 atmosphere (atm). Commonly, the unit torr is used for pressure, where 1 torr = 1 mm Hg (millimeters of mercury), so that atmospheric pressure at sea level equals 760 torr. The SI unit of pressure is the pascal (Pa), so that latm = 760 mm Hg = 760 torr = 1.01325 X 10s Pa (or 101.325 kPa). 

A unit of pressure, symbolized by atm, equal to 760 mmHg or 101,325 pascals (or, newtons per square meter) or 1.01325 bar. At sea level, atmospheric pressure... 

PRESSURE. If a body of fluid is at rest, the forces are in equilibrium or the fluid is in static equilibrium. The types of force that may aci on a body are shear or tangential force, tensile force, and compressive force. Fluids move continuously under the action of shear or tangential forces. Thus, a fluid at rest is free in each part from shear forces one fluid layer does not slide relative to an adjacent layer. Fluids can be subjected to a compressive stress, which is commonly called pressure. The term may be defined as force per unit area. The pressure units may be dynes per square centimeter, pounds per square foot, torr. mega-Pascals, etc. Atmospheric pressure is the force acting upon a unit area due to the weight of the atmosphere. Gage pressure is the difference between the pressure of the fluid measured (at some point) and atmospheric pressure. Absolute pressure, which can be measured by a mercury barometer, is the sum of gage pressure plus atmospheric pressure. 

In the MKS system of units, standard atmospheric pressure is 750 torr and is expressed as 100,000 Pa (N/m2) or 100 kPa. This means that 1 Pa is equivalent to 7.5 millitorr (1 torr = 133.3 pascal). Vacuum, usually expressed in inches of mercury, is the depression of pressure below the atmospheric level, with absolute zero pressure corresponding to a vacuum of 30 inches of mercuiy. 

Because we commonly deal with substances close to atmospheric pressure, it is often convenient to use the unit atmosphere (atm), where 1 atm = 760 Torr exactly. The exact conversion relation between pascals and atmospheres is... 

Typical atmospheric pressure on top of Mt. Everest (29,035 ft) is 265 mm Hg. Convert this value to pascals and to atmospheres. 

Atmospheric pressure at the top of Pikes Peak in Colorado is approximately 480 mm Hg. Convert this value to atmospheres and to pascals. 

Assume that you have an open-end manometer filled with ethyl alcohol (density = 0.7893 g/mL at 20°C) rather than mercury (density = 13.546 g/mL at 20°C). What is the pressure (in pascals) if the level in the arm open to the atmosphere is 55.1 cm higher than the level in the arm connected to the gas sample and the atmospheric pressure reading is 752.3 mm Hg ... 

The pascal represents a very small pressure, and therefore the most common applications, such as tire pressure, will use kilopascals (kPa) instead of Pa. Other units of pressure include the torr (or millimeter of mercury, mmHg), inches of mercury, the atmosphere (atm), and the bar. A torr is an amount of pressure necessary to support a column of mercury 1 mm in height. One atmosphere of pressure is loosely defined by the atmospheric pressure at sea level, but is more precisely defined as the pressure necessary to support a column of mercury 760 mm in height. One bar of pressure is equal to 100 kPa. The relationships between the various units of pressure are given below ... 

Pascal s principle can easily be understood by examining the pressure versus depth equation. Let s assume we have a confined fluid system where the pressure on top of the fluid is atmospheric pressure. Assuming point P1 is at the top of the fluid, the pressure at any point P2 will initially be ... 

Find the pressure (force per unit area) exerted by a 1 m high column of mercury (density = 13.6 kg L-1) on the base of the column, in Pascals (the answer is independent of the width of the column). Compare this to atmospheric pressure. 

A variety of pressure units are in use. These units are related to the column of mercury shown in Figure 6.2. The height of the mercury column in the tube is commonly measured in inches or in millimeters. As you listen to the weather report on the evening news, notice that the atmospheric pressure is given in inches. Where the metric system is in use, millimeters are favored. Millimeters are synonymous with torr, a unit named for the Italian scientist Evangalista Torricelli. Less frequently used units are atmospheres and pascals. The following equation shows the relationship among these various units of pressure. 

For gases, this force can be a factor of their motion or their weight. Atmospheric pressure is caused by the weight of air particles that are attracted toward earth. Inside a sealed container, pressure is exerted by the collisions of particles on the sides of the container. By determining the force of those collisions on a given area, you can determine the pressure exerted by the particles. There are many units that describe pressure. The SI unit of pressure is the pascal, Pa. The kilopascal is a bit more practical as a unit, however, since a pascal is quite small. Other units of pressure include millimeters of Hg (mm Hg), torr, bar, and atmospheres. The relationship between the units is as follows ... 

For many years, atmospheric pressure was measured in millimetres of mercury (mm Hg). In the British Commonwealth and the United States, inches of mercury were used. Standard atmospheric pressure, the pressure of the atmosphere at sea level and 0°C, is 760 mm Hg. More recently, in honour of the work of Torricelli, standard atmospheric pressure has been defined as 760 torr. 1 torr represents a column of mercury 1 mm in height at 0°C. Another common unit for measuring pressure is atmospheres (atm), where 1 atm is equivalent to 760 torr. While mm Hg, torr, and atm are still used to measure pressure, especially in technological and medical applications, the SI units are pascals (Pa) or kilopascals (kPa). 

There is much interest in this superconductor for two reasons. Measurements of the effect of pressure on the material indicate that the onset transition temperature increases to 147 K when the pressure is raised to 230000 times atmospheric pressure (23.5giga Pascal). The result excited many researchers because pressure on a material can be created chemically by replacing some fraction of an ion by a similar ion of smaller radius. The obvious choice in this case was to replace the larger barium with smaller strontium. This had worked with the lanthanum compound discussed earlier. Unfortunately nature is not always so predictable. Replacement of barium by strontium reduced Tc to 127 K instead of increasing it beyond 133 K. The other reason for the interest in this material seems much more important. Resistance measurements in dc magnetic fields have shown... 

A sealed-tube manometer as shown below can be used to measure pressures below atmospheric pressure. The tube above the mercury is evacuated. When there is a vacuum in the flask, the mercury levels in both arms of the U-tube are equal. If a gaseous sample is introduced into the flask, the mercury levels are different. The difference h is a measure of the pressure of the gas inside the flask. If h is equal to 4.75 cm, calculate the pressure in the flask in torr, pascals, and atmospheres. 

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