The molecule though its sizes are also insignificant, has the weight which can be determined. You can express the mass of one molecule of gas both in relative atomic units, and in grams.
It is required to you
- - handle;
- - note paper;
- - calculator;
- - Mendeleyev's table.
Instruction
1. Relative molecular weight is the dimensionless size showing the mass of a molecule concerning 1/12 mass atomof carbon, is measured in relative atomic units.
2. Example 1: Determine the relative molecular mass of CO2. One molecule of carbon dioxide consists of one atom of carbon and two atoms of oxygen. Find in Mendeleyev's table of value of atomic masses for these elements and write down them, having rounded to an integer: Ar(C) = 12; Ar(O) = 16.
3. Calculate the relative mass of molecule CO2, having put the mass of the atoms making it: Îr(CO2) = 12 + 2*16 = 44.
4. Example 2. How to express the mass of one molecule of gas in grams consider on the example of the same carbon dioxide. Take 1 mol of CO2. The molar mass of CO2 is in number equal to molecular: M (CO2) = 44 g/mol. One mol of any substance contains 6.02*10^23 molecules. This number is called constant Avogadro and is designated by a Na symbol. Find the mass of one molecule of carbon dioxide: m(CO2) = M (CO2)/Na = 44/6.02*10^23 = 7.31*10^ (-23) gram.
5. Example 3. You were given gas with a density of 1.34 g/l. It is required to find the mass of one molecule of gas. Under Avogadro's law normal conditions one mol of any gas occupies the volume of 22.4 liters. Having determined weight of 22.4 liters, you will find the molar mass of gas: Mg = 22.4*1.34 = 30 g/mol Now, knowing the mass of one asking, calculate the mass of one molecule similar to an example 2: m = 30/6.02*10^23 = 5*10^(-23) gram.