For saturated steam over liquid Mendeleyev-Klapeyrona's equation is fair. Therefore, knowing temperature, it is possible to calculate density of saturated steam. It increases with temperature increase and does not depend on liquid volume.

## It is required to you

- - paper;
- - calculator;
- - handle;
- - gas pressure (from a statement of the problem or in the table);
- - temperature at which it is necessary to determine density
- - periodic table of Mendeleyev.

## Instruction

1. Write down on paper Mendeleyev-Klapeyrona's equation for ideal gases: (PV=m/M) RT. It can be used also for saturated steam, but as soon as density of gas becomes comparable with a density of saturated steam, this equation cannot be used in calculation – it will show incorrect result. Saturated steam does not submit to other gas laws.

2. Bring density of saturated steam out of the written-down equation. It is equal to the weight divided into volume. Therefore the equation will be transformed: P = (p us. couple/M) RT. From here it is possible to write down a formula for finding of density of saturated steam: p = PM/RT. Here P is gas pressure. Its tabular value usually is given in a statement of the problem and depends on temperature. If it is not given, then find in the table for your temperature. R – it is a universal gas constant, it is equal to 8.31 J / (K*mol).

3. If temperature in degrees Celsius is known to you, then transfer it to degrees Kelvin (it is designated J). For this purpose add 273 to the known temperature as is-273 an absolute zero on Calvin's scale.

4. Find the molar mass of liquid M. It can be calculated by means of the periodic table of Mendeleyev. The molar mass of substance is in number equal to molecular. Find in the table of value of atomic masses of all elements which are contained in substance and increase by amount of the corresponding atoms in a molecule. The sum of the received values will give the molecular mass of substance.

5. Substitute all known values in the last expression. Pressure of P needs to be substituted in Pa. If on a condition it is given in kPa, then increase it for 1000. Transfer molar weight at substitution to kg/mol (divide for 1000) as in the periodic table it is given in g/mol. By means of the calculator calculate value of density of saturated steam. The result turns out in kg/m3.