At the solution of chemical tasks often it is required to learn the molar mass of gas. For determination of molar masses the chemists have different ways – from rather simple which can be executed in educational laboratory (for example, a method of pumping of gas and use of the equation of Mendeleyev-Klapeyrona), to the most difficult and demanding the specialized scientific equipment. However in addition it is possible to determine the molar mass of gas and by the usual table of Mendeleyev.
It is required to you
- - Mendeleyev's table,
- - calculator.
Instruction
1. By definition, molar weight is a weight of 1 mole of a substance, i.e., one portion of substance containing 6*10 in the 23rd degree of particles (Avogadro's number). As particles at the same time both atoms, and ions or molecules can act. Molar weight is to the relative atomic mass of substance, equal in size (or its relative molecular weight if substance has the molecular building).
2. So that to learn the molar mass of the gas having the atomic building it is enough to find his relative atomic mass which is always specified in a table cell near the name of an element in Mendeleyev's table and to round it to the whole value. For example, for oxygen About value of relative atomic mass from a cell equally 15.9994, rounding, we will receive 16 - therefore, molar weight oxygen it is equal of 16 g/mol.
3. Let's consider a case when it is required to find the molar mass of the gas having more complex molecular structure. For this purpose determine by a chemical formula of gas what atoms are its part. For example, according to a formula are a part of a molecule of CO2 carbon dioxide one atom of carbon C and two of atom of oxygen O.
4. Write out relative atomic masses of all chemical elements entering a formula from Mendeleyev's table, and round them to the whole value. With carbon dioxide the rounded value which is already found for oxygen About is equal in the reviewed example to 16; likewise we find the relative atomic mass of carbon C equal in the table 12.011, and, rounding it to whole, we receive 12.
5. Put all rounded values of relative atomic masses of elements taking into account their quantitative ratio in a formula now. For carbon dioxide it will be: 12 (one atom of carbon) + 2*16 (two atoms of oxygen) = 44vy receive number which represents the relative molecular mass of substance in number equal to molar weight is and will be is required value of molar mass of gas, it is enough to substitute the correct dimension only. Thus, in the reviewed example the molar mass of carbon dioxide was 44 g/mol.