In order to understand what the essence of this phenomenon is, and through what values \u200b\u200bit is easy to calculate, you need to refer to school definition. The mass fraction is the value that is the ratio of the atomic mass of the elected element to the product of its atoms in the molecule on the molecular weight. Similar words, it is easy to clarify on the example: if the dish, weighing 500g, should be divided between five comrades, everyone will get to 100 s.
What is a mass fraction and how to calculate it?
This concept is a basic chemistry for the school year, for its designation use the Greek letter "Omega". To type it on the keyboard and insert it into the Internet page, use codes or Ω. In extreme cases, replace this symbol can be written to the letter W, however, it should be remembered that W, also, this resistance measured in watts (or W is an angular frequency, linear acceleration, bulk energy density, depending on the conditions - therefore it is better to use the correct symbol " omega").
This indicator is measured as a percentage, from 0 to 100. There is also an indication of the share if their total number is not 100, but another amount (for example 3 shares of 5, and that to further). In chemical and other types of tasks, the mass fraction is calculated on the basis of the mass conservation law. The formula for finding the desired looks like this:
Examples of using knowledge of the mass fraction
To the material set out become understandable, we will work it in practice. For instance:
- If magnesium, weighing 4.8 grams, reacts with oxygen, is formed 8 grams of a new substance - magnesium oxide. How to determine the amount of oxygen entered into the reaction? In accordance with the law of conservation of mass, the desired element was used in the amount of 3.2 grams. To find mass fractions of all substances, we use the formula above: W magnesium \u003d Magnesium mass, separated by a mass of magnesium oxide \u003d 4.8 g / 8 g \u003d 0.6. To translate this number percentage, multiply it by 100, and we get 60%. Of 100%, which are all substance, we subtract 60% magnesium and we obtain a mass fraction of oxygen - 40%.
- To learn the mass fractions of substances in acid with the H3PO4 formula: we find the relative masses of the elements on the Table D.I. Mendeleev. For n we obtain 1, for p - 31, for o - 16. We fold, in accordance with the number of atoms in the formula (H3PO4) - 3 (H) + (P) + 4 (O) \u003d 98. We find mass fractions of each substance by separate: for H \u003d 3 · 1 · 100% / 98 \u003d 3.06%, for p, respectively, 31.63%, for o \u003d 65.31%. To check the results of the calculations, you need to fold all the numbers and get in the amount of 100%.
To check how well the knowledge is learned, you can use online simulatorsto calculate the mass fraction of the substance. It is also recommended to use a collector-task with chemistry exercises, or its Internet version.
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