Standard temperature and pressure STP

Standard measurements of gases are always given at STP. If no information is given, it will be assumed that the conditions are STP, 

We have already seen (Section 4.3.1) that a mole of any substance, whether the particles are atoms, molecules or formula units, contains 6.02 X 10 particles . What does this mean when we are talking about gases How can we judge 1 mole of gas Experiments have shown that at STP, i.e. at 25 °C and 1 atmosphere pressure, 

By using this fact in combination with the relationship density = massl volume, we can work out how much gas in moles or in grammes is present in any volume under different conditions. It is probably easiest to show this using an example. 

A helium balloon has a volume of 5 dm. How many moles of helium are in the balloon  

---

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 ... 

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. 

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). 

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. 

Assume that 1 kmol of gas occupies 22.4 m3 at standard temperature and pressure (STP). For stage-cut fractions from 0.1 to 0.9, calculate the purity of hydrogen in the permeate, the membrane area and the fractional hydrogen recovery for a single-stage membrane. 

According to the combined gas law, the volume of a given mass of gas can have any value, depending on its temperature and pressure. To compare the quantities of gas present in two different samples, it is useful to adopt a set of standard conditions of temperature and pressure. By universal agreement, the standard temperature is chosen as 273 K (0°C) and the standard pressure is chosen as exactly 1 atm (760torr). Together, these conditions are referred to as standard conditions or as standard temperature and pressure (STP). While there is nothing special about STP, some authors and some instructors find it convenient to use this short notation for this particular temperature and pressure. 

ADCA is a yellow crystalline solid which decomposes to produce a high yield of gas (220-240 cm3/g at standard temperature and pressure (STP)). The gas to which it decomposes consists of 62% nitrogen, 35% carbon monoxide and 3% ammonia and carbon dioxide. Moisture can affect the blowing characteristics of ADCA. 

Any low-molecular-weight organic compounds are normally a gas at standard temperature and pressure (STP) may also be found in the soil solution. These compounds will be produced as a result of the decomposition of organic matter in soil. Many of these will be readily taken up and used by microorganisms and thus their life spans in the soil solution are short. 

For gases and vapors, exposure concentrations are traditionally expressed in parts per million (ppm). The calculation for the ppm of a gas or vapor in an air sample is based on Avogadro s Law, which states that Equal volumes contain equal numbers of molecules under the same temperature and pressure. In other words, under standard temperature and pressure (STP), one gram-molecular weight (mole) of any gas under a pressure of one atmosphere (equivalent to the height of 760 mm mercury) and a temperature of 273 K has the same number of molecules and occupies the same volume of 22.4 liters. However, under ambient conditions, the volume of 22.4 liters has to be corrected to a larger volume based on Charles Law, which states that at constant pressure the volume of gas varies directly with the absolute temperature. Thus, at a room temperature of 25° C, one mole of a gas occupies a volume of 24.5 liters. 

For fixed time assays this most frequently involves the use of standards and a calibration graph. Some methods, e.g. the use of the molar absorbance coefficient in spectrophotometry, do not requite standards and giiNometric methods permit the calculation of molar concentration from the volume of gas (1 gram mole of gas occupies 22.4 litres at standard temperature and pressure, STP). 

A strong normal shock wave is generated in a shock tube tilled with dry air at standard temperature and pressure (STP). The oxygen and nitrogen behind the shock wave tend to react to form nitric oxide. 

The conditions of 0° C temperature and 1 atm pressure may easily be produced in the laboratory such conditions are called standard temperature and pressure (STP). Because the properties of gases vary with both temperature and pressure, many published values are for gases at STP. Note that room temperature differs from standard temperature. 

At standard temperature and pressure (STP) one mole of an ideal gas occupies a volume of 22.4 dm. Therefore, if the number of moles of gaseous products originating from the gunpowder charge is calculated, an estimate can be made of the closed vessel pressure. 

Before you start your hooray-chemistry-is-finally-getting-simple dance, understand that certain conditions apply to this conversion factor. For example, it s true only at standard temperature and pressure (STP), or 0°C and 1 atmosphere. Also, the figure of 22.4 L/mol applies only to the extent that a gas resembles an ideal gas, one whose particles have zero volume and neither attract nor repel one another. Ultimately, no gas is truly ideal, but many are so close to being so that the 22.4 L/mol conversion is very useful. 

In a similar though less diabolical manner, the electrons produced at the anode of a voltaic cell have a natural tendency to flow along the circuit to a location with lower potential the cathode. This potential difference between the two electrodes causes the electromotive force, or EMF, of the cell. EMF is also often referred to as the cell potential and is denoted fj.g,. The cell potential varies with temperature and concentration of products and reactants and is measured in volts (V). The standard cell potential, or E° gn, is the that occurs when concentrations of solutions ire all at 1 M and the cell is at standard temperature and pressure (STP). 

The volume of gas produced during an explosion will provide information on the amount of work done by the explosive. In order to measure the volume of gas generated standard conditions must be established, because the volume of gas will vary according to the temperature at which the measurement is taken. These standard conditions also enable comparisons to be made between one explosive and another. The standard conditions set the temperature at 0 °C or 273 K, and the pressure at 1 atm. These conditions are known as standard, temperature and pressure , stp . Under these standard conditions one mole of gas will occupy 22.4 dm3, which is known as the molar gas volume. The volume of gas V produced from an explosive during detonation can be calculated from its equation of decomposition, where information can be obtained on the amount of gaseous products liberated. Examples for the calculation of V during detonation of RDX and TNT are given below. 

Standard temperature and pressure (STP) are 0°C and 1 atm. The molar volume of an ideal gas under various conditions is given in Table 4.4. 

---