How to learn how to calculate the solute mass fraction of computational chemistry and the calculatio

1 The meaning of the sentence of the mass fraction of the solute itself is to be understood, the expression: the mass of the solute The mass of the solution is multiplied by 100%. The last dissolved is not counted as a solute and cannot be counted as a solution part.

An important factor that interferes with the thinking is the understanding of percentages, and the rest of the above problems is the calculation of chemical equations. In addition, the calculated data placed in the chemical equation must be the data of the pure substance, and the common mistake is to put the mass of the mixture in the chemical equation.

2 Calculation of chemical formulas: The reason why I can't do it is that I can't understand the meaning of the topic and the concept is confused.

Anything that involves "number" is counted directly by looking at the chemical formula. Wherever the word "mass" is involved, the relative atomic mass is used. At the same time, it should be noted that the relative atomic mass is multiplied by the number at the bottom right.

Take a look at this collection of mine.

There is a problem hi me.

Well, memorize the formula first. Doing the question is the key! The most important practice questions at the back of the book are to understand the example questions in the book before doing it. It works better.

The best way is to memorize chemical equations, and when you encounter a problem, you want to reflect, and then go to the set of formulas according to the given, the important problem solving methods you are learning now are the law of conservation of mass, and the breakthrough point is the equation.

Relative molecular mass = relative atomic mass * number of atoms Elemental mass fraction = (relative atomic mass * number of atoms) Relative molecular mass Solution mass = solute mass + solvent mass Solute mass fraction = solute mass Solution mass = solute mass (solute mass + solvent mass) Mass conservation law: total mass of matter before reaction = total mass of matter after reaction Calculation of chemical difference: total mass of matter before reaction - total mass of substance after reaction = mass of gas generated The total mass of the dust spinner material after the reaction - the total mass of the material before the reaction = the mass of the gas participating in the reaction The mass of the solution before the reaction - the mass of the solution after the reaction = the mass of the gas generated or the mass of the precipitate There is also the most important calculation formula --- chemical equation.

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Problem description: Two kinds. Analysis:

The ratio of solute mass to solution mass is called the mass fraction of the solute (expressed in the W table, formerly known as the mass percentage concentration). This is a commonly used representation of the composition of a solution, and the formula is:

Mass fraction of solute = (solute mass solution mass) Li Zhi * 100% = solute mass (solute mass + solvent mass] * 100%.

Example 10 g of sodium chloride dissolved in 90 g of water in the resulting sodium chloride solution.

Mass fraction of solute = 10 100 = 10%.

1.A factory laboratory is equipped with 5000g of 20% hydrochloric acid, and 38% hydrochloric acid is required (what is the volume of density?).

Answer: 5000*20%=x*x=2211ml (approximately equal).

2.If you have 50 g of a 5 Naci solution, and you want to double its mass fraction, you should take ().

a) Add 2 5GNacl solids and (b) Add 25 g of NaA solution with a solute mass fraction of 20.

c) Evaporate the solvent by 25g (d) Evaporate half of the solvent.

Answer: When the solid is added, the mass of the solute increases, and the mass fraction of the solute in the resulting solution is 50gx5 +2 5g 100 :9 5 50g +2 5g (a) is not true.

When the two solutions are mixed, the mass fraction of the solute in the mixed solution is the sum of the masses of the two solutes divided by the sum of the masses of the two solutions: 50g 5 + 25g 20 100: 10 50g + 25g one (b) pair.

When the solvent evaporates, the mass of the solute does not change, and the mass fraction of the solute in the resulting solution is 100 = 10 (c) pairs. After evaporating half of the solvent, the mass of the solvent is 50g-50g 5:23 75g, and the mass fraction of the solute in the obtained solution is 9 5, (d) is incorrect.

Available matching methods: Equations, etc.

The ratio of solute mass to solution mass is called the mass fraction of the solute (expressed in w, formerly known as mass percentage concentration). This is a commonly used representation of the composition of a solution, and the formula is:

Mass fraction of solute = (solute mass solution mass) * 100% = [solute mass (solute mass + solvent mass]*100% mass of concentrated solution mass fraction of concentrated solution mass fraction of dilute solution mass fraction of dilute solution (the mass of solute remains unchanged before and after dilution of the solution).

Solution: Let the mass of carbon dioxide generated be x, and the solute mass fraction of dilute hydrochloric acid used is YCAC3+2HCl=CaCl2+H2O+CO2 (gas symbol) 100 73 44

25*80% 100y x

100/(25*80%)=73/100y=44/xx=

y = A: (1) The mass of carbon dioxide produced is grams.

2) The solute mass fraction of dilute hydrochloric acid used is:

Because 25g contains calcium carbonate, 80% of marble contains calcium carbonate mass = 25g * 80% = 20g

Assuming that the solute mass fraction of dilute hydrochloric acid used is x, the mass of carbon dioxide produced is YCAC3 + 2HCl = CAC2 + H2O + CO2 100 73 44

20g 100g*x y

100 44 = 20g 100g * x x = 100 44 = 20g y y = 1) The mass of carbon dioxide produced is grams;

2) The solute mass fraction of dilute hydrochloric acid used is:

Let the mass of carbon dioxide produced be x; The solute mass fraction of dilute hydrochloric acid used is YCAC3 + 2HCl = CaCl2 + H2O + CO2 100 73 44

25g×80% y x

100:44=25g 80%:x, solution x=100:73=25g 80%:100y, solution y= Answer: The mass of carbon dioxide generated is, and the solute mass fraction of hydrochloric acid used is.

Caco Relative Molecular Mass:;

CO2 relative molecular mass:

HCl relative molecular weight:

CaCo +2HCl = CO2 + GACl2 + H2O Each molecule of calcium carbonate can release 1 molecule of carbon dioxide.

The mass of carbon dioxide is 25*80% 100*44 = each calcium carbonate molecule reacts with 2 hydrochloric acid molecules.

The mass fraction of hydrochloric acid is 25*80% 100*

CaCO3 + 2HCl = CaCl2 + H2O + CO2 (gas symbol) 100 2 * 44

25*80% 100y x

100/(25*80%)=73/100y=44/xx=

y = A: (1) The mass of carbon dioxide produced is grams.

2) The solute mass fraction of dilute hydrochloric acid used is:

Since all the reactions, it proves that all the calcium carbonate is consumed, first find the mass of calcium carbonate that actually participates in the reaction, that is, 25g*80%, and then find the mass of carbon dioxide and the mass of hydrochloric acid that actually participates in the reaction according to the chemical equation, and then divide by 100g is the mass fraction of hydrochloric acid.

20gcaco3 generated.

The consumption quality score is: