The molecular formula of substance shows what chemical elements and in what quantity are a part of this substance. In practice it is defined in various ways as experimental, by means of methods of the quantitative and qualitative analysis, and mathematical.
Instruction
1. Task: learn a molecular formula of alcohol if it was experimentally established that in its composition of 52% of carbon, 13% of hydrogen and 35% of oxygen (on weight), and its couple are heavier than air by 1.59 times.
2. First of all remember that the molecular mass of air approximately equals 29. Therefore, the approximate molecular mass of the studied alcohol is calculated so: 1.59 x 29 = 46.11.
3. Having determined molecular weight, you at the next stage calculate mass fractions of each element which is a part of this alcohol: 0.52 * 46.11 = 23.98 g (carbon contains so much); 0.13 * 46.11 = 5.99 g (hydrogen contains so much); 0.35 * 46.11 = 16.14 g (oxygen contains so much).
4. And knowing the molar mass of each of the listed elements, elementary define amount of their atoms in one molecule of alcohol (using rounding upwards).
5. Having serially divided 23.98 into 12, 5.99 on 1 and 16.14 on 16.14, receive that the molecule of alcohol contains 2 atoms of carbon, 6 atoms of hydrogen and 1 atom of oxygen. Therefore, it is ethanol well familiar to you - ethyl alcohol (C2H5OH).
6. As a result of the carried-out calculations you establish only an empirical formula of an organic molecule - C2H6O. To this formula there correspond two substances belonging to absolutely different classes of chemical compounds at once: ethyl alcohol and methyl air. Thus, if there was no initial instruction that it is about alcohol, your task would be solved only half.
7. Also it is necessary to specify that at calculations rather big accuracy is necessary. Rounding is admissible, and at times and it is necessary (as in the given example), but moderately. For example, the found molecular mass of alcohol (46.11) quite could be taken when calculating for 46.