To find the molar mass of substance, define its chemical formula and by means of the periodic table of Mendeleyev calculate his molecular weight. It is in number equal to the molar mass of substance in grams on mol. If the mass of one molecule of substance is known, transfer it to grams and increase by 6.022•10^23 (Avogadro's number). The molar mass of gas can be found, using ideal gas law.
It is required to you
- Mendeleyev's table, manometer, thermometer, scales.
Instruction
1. Determination of molar mass of substance on a chemical formula. Find elements in the periodic table of Mendeleyev which correspond to atoms of which the substance molecule consists. If the substance molecule one-atomic, then it also is its molar weight. If is not present, find the atomic mass of each element, and put this masses. The molar mass of substance expressed in grams on mol will be result.
2. Determination of molar mass of substance on the mass of one molecule. In case the mass of one molecule is known, transfer it to grams, then increase by quantity of molecules in one pier of any substance which makes 6.022•10^23 (Avogadro's number). Receive the molar mass of substance in grams on mol.
3. Determination of molar mass of gas. Take a cylinder which can hermetically be closed with in advance known volume which transfer to cubic meters. By means of the pump pump out from it gas, and weigh an empty cylinder on scales. Then fill it with gas which molar mass is measured. Again weigh a cylinder. The difference will be equal in the mass of the empty and pumped gas cylinder to the mass of gas, express it in grams. By means of the manometer measure gas pressure in a cylinder, for this purpose attach it to an opening for pumping gas. It is possible to use a cylinder with the built-in manometer at once quickly to control pressure indicators. Measure pressure in pascals.
4. Wait some time in order that gas temperature in a cylinder was equal to ambient temperature, and measure it by the thermometer. Transfer temperature indicator from degrees Celsius to kelvins for what add number 273 to the measured value. Increase the mass of gas by temperature and a universal gas constant (8.31). Consistently divide the received number into values of pressure and volume (M=m•8.31•T/(P•V)). The molar mass of gas in grams on mol will be result.