To count the molar mass of substance, define its chemical formula. By means of Mendeleyev's table find the atomic mass of each of the substances which are a part of a molecule of the studied substance and then find their sum, it also will be value of molar mass of substance. If the mass of one molecule is known, increase it by Avogadro's number. The molar mass of gas can be found through Klapeyrona-Mendeleyev's equation.
It is required to you
- For carrying out measurements and calculations take Mendeleyev's table, scales, the manometer the thermometer.
Instruction
1. Finding of molar mass of substance Determine a chemical formula of the studied substance by its chemical formula. By means of Mendeleyev's table find the atomic mass of each element entering a substance molecule. If it is several identical atoms, then increase the atomic mass of this element by number of atoms. Put the received values and as a result receive molar weight in grams on mol. If substance simple, then just find its atomic mass in Mendeleyev's table, it will be equal to his molar weight.
2. Determination of molar mass of substance the mass of one molecule in grams is known for the mass of a molecule If, increase it by Avogadro's 6.022•10^(23) number which is equal to quantity of molecules in one mole of a substance. The molar mass of substance in grams on mol will be result. Having found it in Mendeleyev's table, if necessary define substance if it simple (consists of a one-atomic molecule).
3. Determination of molar mass of gas Take a vessel of the known volume and start in it some mass of gas. For this purpose at first pump out gas from it, and weigh, and then pump gas, and again weigh. After that measure gas pressure in pascals by means of the manometer and its temperature in kelvins by the thermometer. That to transfer degrees Celsius to kelvins, add to them 273. To find molar weight, having transformed Klapeyrona-Mendeleyev's equation, take value of mass of gas in grams, increase it by temperature and number 8.31 which is a universal gas constant. Consistently divide the turned-out number into pressure and volume in cubic meters (M=m•8.31•T/(P•V)). The molar mass of gas in grams on mol will be result.