Molar volume at standard temperature and pressure

Skill 2.1a-Calculate molar mass, mass, number of particles, and volume, at standard temperature and pressure (STP) for elements and compounds... 

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). 

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). 

There are ways other than density to include volume in stoichiometry problems. For example, if a substance in the problem is a gas at standard temperature and pressure (STP), use the molar volume of a gas to change directly between volume of the gas and moles. The molar volume of a gas is 22.41 L/mol for any gas at STP. Also, if a substance in the problem is in aqueous solution, then use the concentration of the solution to convert the volume of the solution to the moles of the substance dissolved. This procedure is especially useful when you perform calculations involving the reaction between an acid and a base. Of course, even in these problems, the basic process remains the same change to moles, use the mole ratio, and change to the desired units. 

Avogadro s principle tells us that equal volumes of gases, at equal temperatures and pressures, contain an equal number of particles. It is from this principle that chemists have developed the concept of the molar volume of gases. It has been determined that one mole of any gas at standard temperature and pressure (a temperature of 273 K and 101.3 kPa of pressure) will occupy 22.4 dm3 of volume. This allows us to determine the number of moles in a gas, provided we know the volume, temperature, and pressure of the sample. 

The volume occupied by a mole of gas at standard temperature and pressure, STP, is referred to as the standard molar volume. It is nearly constant for all gases (Table 12-3). 

Molar volume. The volume of one mole of a gas measured at standard temperature and pressure 22.4 L. 

In the laboratory tests, two gas mixtures at two space velocities were used. Each gas mixture contained 1% CO, 250 ppm (molar) hydrocarbon, 2.5% 02, and 10% H20 the remainder was N2. The hydrocarbon was propane or propylene. The flow rate was 5000 cm3/min at standard temperature and pressure (STP). With a catalyst bed of 20 cm3 (% X 2 in.), the gas hourly space volume (GHSV) at STP was 15,000/hr with a bed of 2 cm3 (7/s X in.), it was 150,000/hr. The test consisted of lining out the system at 538°C inlet, and following the temperature-conversion profiles while the reactor cooled until the conversions of both HC and CO were below 25%. Lined-out conversions were then obtained at 288°C and 538°C. 

Thinking it Through It is not a common practice on ACS exams, but do not assume that all information provided in a question is actually essential to its solution. Rather, decide on a route to the solution that will be the most expedient. Given that 6.25 L of Ni(CO)4fgJ form at standard temperature and pressure conditions, the molar volume of 22.4 L can be used as a conversion factor to find the number of moles of Ni(CO>4 present. Then the coefficients in the balanced chemical equation can be applied, observing that one mole of Ni(CO)4 reacts to produce one mole of Ni. The atomic molar mass for nickel can then be used to find the number of grams of Ni present. 

At standard temperature and pressure the molar volume of CI2 and NH3 gases are 22.06 L and 22.40 L, respectively, (a) Given the different molecular weights, dipole moments, and molecular shapes, why are their molar volumes nearly the same (b) On cooling to 160 K, both substances form crystalline solids. Do you... 

One mole of any gas contains the same number of molecules (Avogadro s number = 6.02 X 10 ) and by Avogadro s law must occupy the same volume at a given temperature and pressure. This volume of one mole of gas is called the molar gas volume, V . Volumes of gases are often compared at standard temperature and pressure (STP), the reference conditions for gases chosen by convention to be 0°C and 1 atm pressure. At STP, the molar gas volume is found to be 22.4 L/mol (Figure 5.12). 

For ideal gases, the molar volume is given by the ideal gas equation. This is a good approximation for many common gases at standard temperature and pressure. For crystalline solids, the molar volume can be determined by determining the unit cell volume (Veeu) calculated from unit cell parameters that are determined by x-ray crystallography. 

Table 5.1 Selected properties and heating values of gases occurring in gasification systems [1] (HHV - higher heating value, LHV - lower heating value, M - molar mass, / (STP) - density at standard temperature and pressure, Vmoi-molar volume).

The standard molar volume 22.4 L/mole is applicable at standard temperature and pressure STP. 

The numerical value of the collision theory value rate constant, previously calculated for the NOj + CO reaction (3.11 dm moL sec 0 corresponds to the typical values calculated for the pre-exponential factors of gas-phase bimolecular reactions. Dividing this value by the molar volume of an ideal gas at standard temperature and pressure (22.421 dm moL ), we obtain a relaxation rate, which is approximately = 10 ° atm sec at TTi K. This implies that the mean free time between collisions of molecules of an ideal gas is 0.1 nsec, and that the corresponding collision frequency is 10 ° see . Some caution must be made in using these values, since molecules interact with a range of velocities and instantaneous inter-molecular distances, such that there is no single collision frequency, but... 

When water vapor condenses onto a surface, this surface will be warmed and the surrounding air cooled. In the atmosphere, condensation produces clouds, fog and precipitation. Water vapor will condensate also on surfaces, when the temperature on that surface is below the dew point temperature of the atmosphere. Water vapor is lighter or less dense than dry air and therefore it is buoyant with respect to dry air. The molecular mass of water is 18.02 g/mol, the average molecular mass of air (79% N2,21% O2) is 28.57 g/mol. Avogadro s law states that at standard temperature and pressure the molar volume of a gas is 22.4141/mol. From that we can calculate the density p = m/V and And the values water vapor 0.8 g/1, dry air 1.2 g/1. 

Standard-state fugacities at zero pressure are evaluated using the Equation (A-2) for both condensable and noncondensable components. The Rackett Equation (B-2) is evaluated to determine the liquid molar volumes as a function of temperature. Standard-state fugacities at system temperature and pressure are given by the product of the standard-state fugacity at zero pressure and the Poynting correction shown in Equation (4-1). Double precision is advisable. 

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