Pressure standard temperature and

It is veiy important to understand the general aspects of gas pressure, its measurements, and calibrations. Pressure is force exerted over imit area. The unit of pressure is pascal (Pa) which is equivalent to kg/(m.s ). In chemistry, we usually use a mercury-based barometer to measure the pressure. The unit is millimeter of mercury (mmHg). This is the same as the unit torr. Another unit commonly used to denote pressure is atmosphere (atm). You should be able to convert these units back and forth as required. 

Gases can be compressed or expanded by adjusting the temperature and other conditions that prevail. In order to standardize the quantities of gases measured and conveyed, arbitrary reference conditions called standard temperature and pressure (STP) have been chosen and internationally accepted. The specific values of temperature and pressure at STP are 0 C (273 K) and 1 atm (760 mmHg). 

You should know what STP is, because in many questions and passages, the actual temperature and pressure situations will not be explicit. Rather, they will say, for example, that the reaction was undertaken at standard temperature and pressure. This means, you have to automatically know that they are talking about the temperatures corresponding to STP reference conditions, which you already know. 

In real-world analytical situations, pressure and temperature conditions can vary widely. Air samples for pollutant analysis, for example, can be taken on cold days or hot days, on a high mountain where the air is thin (i.e., lower pressure) or at sea level. The volume of the air sample depends on the pressure and temperature, as discovered in our discussion of Boyle s and Charles laws. 

This volume, in turn, is needed in the calculation of the concentration level of the pollutant in the air, which is the critical factor in knowing whether the polluted air is hazardous to our health. The bottom line is that the volume of air that we sample needs to be corrected to standard conditions of temperature and pressure so that we may accurately compare the results of the air analysis with accepted threshold safety limits. 

Another example of this problem is if the measurement of a gas volume is needed to prove a point in a research experiment. Researchers in Denver, Colorado, (which is at low pressure) working at a laboratory temperature of 25°C will report one volume for their experiment while a researcher in Los Angeles, California, (at sea level) working at a laboratory temperature of 20°C will report a different volume, simply because conditions of temperature and pressure varied. However, if their volumes are corrected to an accepted standard for temperature and pressure, their answers should be the same, all other conditions being equal. 

Scientists have therefore adopted specific pressure and temperature values that represent these standard conditions. Standard pressure is 760 torr, or 1 atm. Standard temperature is 0°C, or 273.15 K. These values are referred to as standard temperature and pressure (STP). 

Boyle s law and Charles law show how the volumes of gases depend on their pressures and temperatures. To ensure there is a level playing field when comparing volumes of two or more gases, all gases must be compared at the same temperature and pressure. For this purpose, a temperature of 0°C and a pressure of 1.00 atm have been universally accepted as the standard temperature and pressure (STP) for gases. 

The volume of one mole of any gas at STP is 22.4 L. This is the standard molar volume of gases, and remember, this is true for all gases. 

Approach 2 Convert 1.00 mole of C02 to mass, 44.01 g of C02, and then restate the molar volume of C02 like this 44.01 g of C02 occupies 22.4 L at STP. Mass can be used in place of moles in Avogadro s law as long as both masses are of the same compound. Remember, the mass of a compound is directly proportional to the moles of that compound. 

Answer Both approaches show that 30.8 g of CO2(g) have a volume of 15.7 L at STP. 

The combined gas law unites Boyle s law and Charles law in a single equation  

---

Reservoir fluids (oil, water, gas) and the rock matrix are contained under high temperatures and pressures they are compressed relative to their densities at standard temperature and pressure. Any reduction in pressure on the fluids or rock will result in an increase in the volume, according to the definition of compressibility. As discussed in Section 5.2, isothermal conditions are assumed in the reservoir. Isothermal compressibility is defined as ... 

TABLE 2.19 Factors for Reducing Gas Volumes to Normal (Standard) Temperature and Pressure (760 mmHg)... 

Fowlef measured the turbidity of air at Mt. Wilson, California, on a clear day in 1913. Values of rx for dry air at different wavelengths are tabulated below, where x is essentially the thickness of the atmosphere corrected to standard temperature and pressure (STP) conditions ... 

AH gas volumes at standard temperature and pressure. To convert to cal, divide by 4.184. 

The solubihty coefficient must have units that are consistent with equation 3. In the hterature S has units cc(STP)/(cm atm), where cc(STP) is a molar unit for absorbed permeant (nominally cubic centimeters of gas at standard temperature and pressure) and cm is a volume of polymer. When these units are multiphed by an equihbrium pressure of permeant, concentration units result. In preferred SI units, S has units of nmol /(m GPa). 

Carbonation can be measured ia terms of volumes of carbon dioxide dissolved ia one Hter of beverage at a standard temperature and pressure (0°C, 101.3 kPa = 1 atm). One Hter of carbon dioxide dissolved ia one Hter of beverage has a carbonation volume of one. 

Explosibility and Fire Control. As in the case of many other reactive chemicals, the fire and explosion hazards of ethylene oxide are system-dependent. Each system should be evaluated for its particular hazards including start-up, shut-down, and failure modes. Storage of more than a threshold quantity of 5000 lb (- 2300 kg) of the material makes ethylene oxide subject to the provisions of OSHA 29 CER 1910 for "Highly Hazardous Chemicals." Table 15 summarizes relevant fire and explosion data for ethylene oxide, which are at standard temperature and pressure (STP) conditions except where otherwise noted. 

For combustion with air at standard temperature and pressure. These flame temperatures are calculated for 100 percent theoretical air, disassociation considered. Data from Gas Engineers Handbook, Industrial Press, New York, 1965. 

With gases, flow rates must be available at standard temperature and pressure as well as actual temperature and pressure. The range of gas flow must be given, as well as whether the mixer is to be operated at full horsepower for all gas ranges or operated with the gas on. 

P23 Adsorption - Resin concentrations (at standard temperature and pressure) as ... 

Barometric pressure at standard temperature and pressure = 101.325 kPa Standard temperature and pressure (STP) = 0 °C at 101.325 kPa (also known as normal temperature and pressure)... 

Normal temperature and pressure (NTP) See Standard temperature and pressure (STP). 

Gas The state of matter characterized by complete molecular mobility and unlimited expansion at standard temperature and pressure. 

This is defined as the amount of heat liberated when unit volume (or unit mass) of the gas is burned at a standard temperature and pressure. It is usually expressed in terms of megajoules per cubic meter at 15°C and lOlbmbar, i.e. MJ/s m dry or megajoules per kilogram. Typical... 

Thus chemists have accepted 0°C and one atmosphere as convenient standard conditions. These conditions, 0°C and 760 mm pressure, are called standard temperature and pressure and are abbreviated STP. 

Carbon monoxide (CO) is a colorless and odorless gas molecule. This inorganic compound, at standard temperature and pressure, is chemically stable with low solubility in water but high solubility in alcohol and benzene. Incomplete oxidation of carbon in combustion is the major source of environmental production of CO. When it burns, CO yields a violet flame. The specific gravity of CO is 0.96716 with a boiling point of -190°C and a solidification point of-207°C. The specific volume of CO is 13.8 cu ft/lb (70°F). 

At standard ambient temperature and pressure (SATP), which means exactly 25°C (298.15 K) and exactly 1 bar, the conditions commonly used to report data in chemistry, the molar volume of an ideal gas is 24.79 L-mol l, which is about the volume of a cube l ft on a side (Fig. 4.15). The expression standard temperature and pressure (STP) means 0°C and 1 atm (both exactly), the conditions formerly used to report data and still widely used in some calculations. At STP, the molar volume of an ideal gas is 22.41 I.-mol1. Note the slightly smaller value the temperature is lower and the pressure is slightly higher, and so the same amount of gas molecules occupies a smaller volume than at SATP. 

---