Guide
1
Knowing formula gas , its molar mass can be calculated by an elementary calculation.Take carbon dioxide.Its formula - CO2.So its molar mass is as follows: 12 + 32 (molar mass of oxygen based on the index "2») = 44.
2
Well, if you need to calculate the molar mass an unknown gas , located insome kind of confinement such as a sealed bottle?Here we come to the aid of the universal equation of Clapeyron-Mendeleev, describing the state of the "ideal gas ».Of course, none of the gas does not meet the "ideal", but at a pressure a
nd temperature, slightly different from the normal equation is very convenient for calculations.And the resulting uncertainty in the calculations is very small and it can be safely ignored.
3
universal equation has the form: PV = MRT / m, where P - pressure gas in Pascals;
V - its volume in cubic meters;
M - actual weight gas ;
m - its molar mass;
R - the universal gas constant;
T - Temperature gas in degrees Kelvin.
4
You will see that the molar mass is calculated by the formula MRT / PV.For example, it is necessary to find the molar mass gas, if it is known that 3 kilograms of gas are in a sealed container volume of 1.7 cubic meters at a pressure of 100,000 Pa and a temperature of 27 degrees Celsius.
5
Substitute known values ​​in this formula, of course, do not forget to first convert into a single system of values.Otherwise it will complete nonsense.3.0 * 8.31 * 300/170000 = 0.04399 kg / mol.
6
Well, since the molar mass of the substance measured in grams per mole, multiply the result by 1000 and get an answer: the molar mass of the gas , located under these conditions is equal to 43.99 grams / mole oras rounded - 44 gram / mole.That is the same carbon dioxide.