Molar volume of a gas

The interaction forces which account for the value of a in this equation arise from tire size, the molecular vibration frequencies and dipole moments of the molecules. The factor b is only related to the molecular volumes. The molar volume of a gas at one atmosphere pressure is 22.414 ImoD at 273 K, and this volume increases according to Gay-Lussac s law with increasing... 

Since the molar volume of a gas is much larger than the molar volume of the liquid phase, the Clapeyron equation can be reduced to... 

Compressing ammonia gas under high pressure forces the molecules into close proximity. In a normal gas, the separation between each molecule is generally large - approximately 1000 molecular diameters is a good generalization. By contrast, the separation between the molecules in a condensed phase (solid or liquid) is more likely to be one to two molecular diameters, thereby explaining why the molar volume of a solid or liquid is so much smaller than the molar volume of a gas. 

Compressing a gas brings the particles into close proximity, thereby increasing the probability of interparticle collisions, and magnifying the number of interactions. At this point, we need to consider two physicochemical effects that operate in opposing directions. Firstly, interparticle interactions are usually attractive, encouraging the particles to get closer, with the result that the gas has a smaller molar volume than expected. Secondly, since the particles have their own intrinsic volume, the molar volume of a gas is described not only by the separations between particles but also by the particles themselves. We need to account for these two factors when we describe the physical properties of a real gas. 

Background Avogadro s law (Vin2 = V2ni), where moles, n = mw (grams/mole) exPresses the relationship between molar mass, the actual mass and the number of moles of a gas. The molar volume of a gas at STP, VSTP is equal to the volume of the gas measured at STP divided by the number of moles VSTp = pp. Dalton s Law of Partial Pressure (Ptotai = Pi + P2 + P3 +. ..) and the derivation, Pi = pp Ptotai will also be used in this experiment to predict the volume occupied by one mole of hydrogen gas at STP. 

The values of P, T, and n may be used to determine the volume of a gas. If this volume is to be used with Avogadro s law of 22.4 L/mol, the combined gas law must be employed to adjust the volume to STE This equation will use the measured values for P and Talong with the calculated value of V. These values are combined with STE conditions (0°C (273.15 K) and 1.00 atm) to determine the molar volume of a gas. 

Unformnately, when temperamres other than 0°C and 100°C are measured, the value obtained depends on the property used to measure it and, for the same property, depends on the substance whose property is measured. However, when the product of the pressure and the molar volume of a gas A, which is a quantity that changes in a monotonic fashion with changes of temperature, is measured at a series of pressures, and these values are extrapolated to a limit at zero pressure, the fimit is the same for all gases at a given temperature. This phenomenon is illustrated for several gases in Figure 3.1. 

The value of the gas constant R can be calculated from a knowledge of the standard molar volume of a gas. Since 1 mol of a gas occupies a volume of... 

The Standard Molar Volume of a gas is the volume that exactly 1 mole of an ideal gas occupies under STP conditions. The standard molar volume of a gas is 22.71 L. 

In Fig. 2, the chemical potential curves of Fig. la are shown for two different pressures. Because the molar volume of a gas is greater than that of condensed phases, the chemical potential of the gas is increased much more than those of liquid or solid by increasing pressure. The boiling point and sublimation point therefore increase with pressure. The molar volume of the liquid and solid are comparable, and either one may be larger. As a result, the melting point may either increase or decrease with pressure. 

From the chemical equation for the reaction and using the relative formula masses together with the molar volume of a gas it is possible to predict the amounts of magnesium sulfate and hydrogen that arc produced when 24gof magnesium is reacted with excess sulfuric acid. 

Continuing to consider pure substances, the molar volume of a gas, Vm>g ... 

Determination of the molar volume of a gas barometer, beaker, Erlenmeyer flask, test tubes, graduated cylinder, clamp, analytical balance, thermometer, rubber tubing... 

Based on Avogadro s law, one mole of a gas occupies the same volume as one mole of another gas at the same temperature and pressure. The molar volume of a gas is the space that is occupied by one mole of the gas. Molar volume is measured in units of L/mol. You can find the molar volume of a gas by dividing its volume by the number of moles that are present (- ). Look at the Sample Problem below to find out how to calculate molar volume. Then complete the following Thought Lab to find the molar volumes of carbon dioxide gas, oxygen gas, and methane gas at STP. 

The accepted molar volume of a gas at STP is 22.4 L/mol. Use this value to calculate the percent error in your experimental data for each gas. 

Use the ideal gas law to calculate the molar volume of a gas at standard ambient temperature and pressure (SATP). The conditions for SATP are 298 K and 100 kPa. 

As you learned in the last section, the molar volume of a gas is defined as the space that is occupied by one mole of the gas. It is always given in units of L/mol. 

In this section, you learned how to use Gay-Lussac s law to calculate volumes of gases in a gas reaction. You also learned how to use the ideal gas law to find the volumes of gases used or produced in reactions. Building on Dalton s law of partial pressures, from Chapter 11, you learned how to calculate the molar volume of a gas collected over water. Finally, you learned, first-hand, how to produce hydrogen gas in a laboratory. 

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