during the chemical reaction does not always work that theoretically planned, at least quantitatively.This is usually due to the difficult conditions of the reaction - the non-ideal temperature, lack of contact with the catalyst and a chemical impurity reagents.In this case, the chemists use the phrase "the mass fraction of output."
This concept includes a specific amount - a percentage virtually obtained with respect to what should have been chemically happen.Denoted by the letter "omega".This value should be considered, students often forget to count a small percentage.Particularly disappointing is on the different kinds of testing - the right train of thought, and a standard examination would allow most of the points for the task to count - and in testing on such trifles "catch."Even given the option of taking into account the response of such an error.It is easy to get caught.So before solve the problem, check - whether the parameter "mass fraction of output."
There are other, similar-sounding concepts.The term "mass fraction" can be combined with other terms.And then it turns out, for example, the proportion of the ore.That is, you have a piece of material in which only a certain part can react.And it should be taken into account in the calculations, otherwise run the risk of falling into the trap, as well as the concept of "mass fraction of output."Too many are caught and successfully.Caution
The condition is the mass fraction of the element in the mix?This means that its atoms make up a certain percentage by weight in substance.In principle, chemists and fans of the mass fraction of complex solutions can be useful for calculations on reaction equations.Another practical value of this information may have if you need to set a formula of matter.Just be careful - there are substance-isomers and substances with similar proportional formula.You to establish the exact formula required chemical reactions.But it is not the level of the school, and competition for chemistry.
In fact, usually all the tasks a lot easier to check students knowledge of elementary formulas and the ability to perform simple mathematical operations, do not forget about the number of atoms per molecule.How do you calculate the mass fraction of the element?In the table find the atomic weight of the desired item, multiply by the exact number of atoms in the molecule.This is the numerator.A denominator must be the molecular weight of the whole substance of the formula unit, i.e. your element with the required multipliers and all other elements of mass multiplied by the number in the molecule.For example, the molecular weight of the water molecule - 16 (oxygen), the addition of two atoms of hydrogen (1 + 1).Total 18. Mass fraction of a hydrogen element is simple: divide 2 na18.Pri need to multiply by one hundred percent, but in fractions of a unit is also possible.Similar to the case and in more complex formulas when three or more elements.
Mass fraction of the concept applies for solutions.Numerator - the mass dissolved, the denominator - the weight plus the weight of the solvent dissolved.
If you pay attention and understand all of the possible cases, you do not have the words in the elementary.And do not be hurt because of the low points, when everything seems to be decided, but the result is not happy.Just do not miss the sight of these terms.Study and practice on concrete problems.When nabete hand, difficulties are all in the past.
