Chemistry calculation questions in junior high school give me answers quickly Questions you found on

1) Mass of carbon dioxide = 6g+

2) Let the mass of calcium carbonate be x and the mass of dilute hydrochloric acid be y, then there is:

caco3 + 2hcl =cacl2+h2o+co2x y

100:x=73:y=

The solution is x=5g, y=

Therefore, the mass fraction of calcium carbonate in the sample is: 5g 6g *100% = 3) The solute in dilute hydrochloric acid is, and the mass of the whole solution is: 19g So, in the dilute hydrochloric acid solution, the mass fraction of the solute is: *100% = Hope Ha!

Special topic exercises in chemical calculations for junior high school students.

Calculation is a compulsory content in the high school entrance examination, and it is the last question of the test paper, and it will also be interspersed with experimental questions and ** edition questions, accounting for about 4 7 points. Typical question types in the middle school entrance examination: chemical reaction equations and equations in solution, metal and acid reaction to produce hydrogen, diagrammatic, image analysis and calculation.

It is mainly divided into three categories: calculation according to chemical formula, calculation according to chemical equation, and calculation of solution.

1. Calculated according to the chemical formula.

Basic knowledge: Relative molecular mass The sum of the atomic masses (number of atoms relative to atomic mass) of each atom contained in the molecule;

Elemental mass ratio = mass fraction ratio of element, number of atoms ratio, relative atomic mass ratio;

The mass fraction of the element The relative atomic mass of the element The number of atoms The relative molecular mass.

Question type: Calculate the ratio of the number of atoms of each element in a molecule.

Calculate the relative molecular weight of the molecule.

Calculate the mass ratio of each element in the molecule.

Calculate the mass fraction of an element in a molecule.

Given the mass of the substance, the mass containing an element is calculated.

Chemistry is the study of the composition, structure, properties and changes of substances to generate a large number of white smoke text expressions people's education edition junior high school third volume physics monthly exam papers, to bring answers.

1. Multiple choice questions (only one for each question; （

Sodium carbonate is added to produce a gas with a net weight gain.

For the balance to be balanced, the other side must also gain weight.

We know that when iron is added, hydrogen is produced, and there is a net increase.

Now a net increase is required, then the mass of iron needs to be added as.

1. The group carries the air and collapses into the solute.

50*a%+x=(50+x)*2a%

x=50a/(100-2a)

2. Evaporative dissolving concealer.

50*a%=(50-y)*2a%

y=25g

The composition of clarified lime water is Ca(OH)2, carbon monoxide is almost insoluble in water, no reaction with water and lime, and the white precipitate is calcium carbonate generated by the reaction of carbon dioxide and Ca(OH)2. So:

CO2 + Ca(OH)2 = CaCO3 (white precipitate) + H2O44 100 (molecular weight).

x 10 (mass, grams).

CO2: x = grams.

co=grams. Co Percentage =

o2 + ca(oh)2 == caco3 + h2o44 100

xg 10g

So, 44 xg == 100 10g

x = So, carbon dioxide has grams.

So, there are grams of carbon monoxide.

That's the right question.

According to the balance before and after the reflection, it can be seen that the reduced mass after the reflection is all CO2, CaCO3 == Cao + CO2

100 56 44x

x = 10 purity = 10 12 =

Sorry, the mass of the solid reduction is the mass of the CO2 generated, that is, the mass of CaCO3 of the gram reaction is x grams, and the mass of CaCO3 == high temperature == Cao + CO2

xg。。。100/xg=56/

x = 10g1 > mass g of carbon dioxide generated -

2> The purity of this limestone sample is 10 12=

The mass of carbon dioxide produced is.

CaCO3 == High temperature == Cao + CO2

xgx=10g

What is the purity of this limestone sample 10 12=Do the math for yourself Hehe.