Relative density of gas

Relative density of gas - comparison of relative molecular or molar mass of one gas with the same value of another gas. As a rule, it is determined with respect to the lightest gas - hydrogen. Also, gases are often compared to air.

In order to show which gas is chosen for comparison, an index is added before the relative density symbol of the researcher, and the name is written in parentheses. For example, DH2 (SO2). This means that the density of sulfur oxide was calculated for hydrogen. This is read as "the density of sulfur oxide over hydrogen."

To calculate the gas density in hydrogen, it is necessary to determine the molar masses of the gas and hydrogen under investigation using a periodic table. If it is chlorine and hydrogen, the indicators will look like this: M (Cl2) = 71 g / mol and M (H2) = 2 g / mol. If the density of hydrogen is divided by the density of chlorine (71: 2), the result is 35.5. That is, chlorine is 35.5 times heavier than hydrogen.

Relative density of gas from external conditions does not depend. This is explained by the general laws of the state of gases, which reduce to the fact that changes in temperature and pressure do not lead to a change in their volume. With any changes in these indicators, measurements are made exactly the same.

To determine the gas density, an experimental test will require a flask, where it can be placed. The flask with gas must be weighed twice: the first time - pumping out all the air from it; The second - filling it with the gas being investigated. Also it is necessary to measure the volume of the bulb in advance.

First, you need to calculate the mass difference and divide it by the volume of the bulb. As a result, the gas density will be obtained from the given conditions. Using the equation of state, it is possible to calculate the desired index under normal or ideal conditions.

The density of some gases can be determined from the summary table, in which there is ready information. If the gas is stored in a table, then this information can be taken without any additional calculations and use of formulas. For example, the water vapor density can be determined from the table of water properties (the Rivkin SL Handbook, etc.), its electronic counterpart or by means of programs such as WaterSteamPro and others.

However, in different liquids equilibrium with the vapor occurs at different densities of the latter. This is due to the difference in the forces of intermolecular interaction. The higher it is, the sooner the equilibrium will come (for example, mercury). In volatile liquids (for example, ether), equilibrium can occur only with a significant vapor density.

Density of various natural gases varies from 0.72 to 2.00 kg / m3 and above, relative - from 0.6 to 1.5 and above. The highest density of gases with the highest content of heavy hydrocarbons is H2S, CO2 and N2, and the lowest for dry methane.

The properties of natural gas are determined by its composition, temperature, pressure and density. The last indicator is determined by laboratory methods. It depends on all the above. Determine its density can be different methods. The most accurate is weighing on a precise scale in a thin-walled glass bottle.

The air density is greater than the same index of natural gases. In practice, this ratio is taken as 0.6: 1. Static air pressure decreases faster than gas. At a pressure of up to 100 MPa, the density of natural gas is capable of exceeding 0.35 g / cm3.

It is established that an increase in the density of natural gas can be accompanied by an increase in the temperature of hydrate formation. A low-density natural gas forms hydrates at a higher temperature than gases with increased density.

In the gas industry, density meters are just beginning to be used and there are still many questions that are related to the specifics of their operation and verification.