Sometimes before researchers there is such task: how to define amount of atoms of any given substance? Originally it can seem exclusively difficult, amount of atoms even in a tiny sample of any substance just grandiose. How to count them?
Instruction
1. Let's assume, you should count amount of atoms in a piece of pure metal - for example, iron, copper or even gold. Yes, present yourself on the place of the great scientist Archimedes to which the tsar Giyeron gave a completely different assignment, having told: "You know, Archimedes, in vain I suspected the jeweler of fraud, the crown appeared from pure gold! Our royal majesty needs to know now how many in it gold atoms".
2. The task, naturally, would cast the real Archimedes into a stupor though he also was a genius. And you would cope with it in no time. At first it is necessary to weigh a crown precisely. Let's assume, it would weigh exactly 2 kg, that is 2000 grams. Then according to Mendeleyev's table establish the molar mass of gold (about 197 grams/mol.) For simplification of calculations slightly round up – let there will be 200 grams/mol. Therefore, in the ill-fated crown of exactly 10 moths of gold. And then take universal number of Avogadro (6.022х1023), increase by 10 and with a celebration refer result to the tsar Giyeron.
3. And if it is necessary to count amount of atoms of gas? The task is slightly more difficult, but too easily solvable. It is necessary only with a sufficient accuracy to take temperature, volume and pressure of gas.
4. And then use well familiar equation of Mendeleyev-Klapeyrona: PV = MRT/m. Pay attention that M/m is nothing else as the number of moles of this gas as M – its actual weight, and m – molar.
5. Substitute sizes known to you in PV/RT fraction, increase the found result by universal number of Avogadro (6.022*1023) and receive amount of atoms of gas at the set volume, pressure and temperature.
6. And if it is required to count amount of atoms in a sample of complex substance? And there is nothing especially difficult. Weigh a sample, then write its exact chemical formula, by means of Mendeleyev's Table specify the molar mass of each component and calculate the exact molar mass of this complex substance (having considered if necessary indexes of elements).
7. And then learn number of moles in the studied sample (having divided the mass of a sample into molar weight) and increase the received result by the size of number of Avogadro.