When the students in the interest group visited a chemical factory, they became interested in one of

After the reaction of the first solution, the gram precipitate is Cu(OH)2, and the mass of copper in the filter residue is x grams.

It is obtained from the conservation of the mass of the copper element:

cu－－－cu(oh)2

xx g) because g) g), indicating that there is also an excess of iron powder in the filter residue.

The excess iron powder in the filter residue is: grams).

Let the iron powder reacted with copper sulfate be y grams.

fe－－－cu

yy grams) then the iron powder that reacts with sulfuric acid is: grams).

Let the sulfuric acid reacted with gram iron powder be z grams.

fe－－－h2so4

Z g) so the mass fraction of H2SO4 in the solution is:

Please ask upstairs: FE excess 18, I don't understand this, since there are 4 grams of excess iron powder in the filter residue, indicating that the sulfuric acid has been reacted, where does this gram of iron powder come from? And then I suspect that the answer is wrong.

The obtained precipitate is Cu(OH)2, and the maximum amount of m g Cu can be produced by adding iron powder, and Cu is conserved.

cu=》cu（oh）2

m 64 = m = and the mass of the filter residue is grams, indicating that there is 4 gFe in the filter residue and there is an excess of Fe.

Set the FE to change CU has x grams, according to the FE substitution CU equation, there is.

x 56 = x = so Fe that reacts with sulfuric acid has.

Let the sulfuric acid have y grams, according to the equation, there is.

y = so the mass fraction of H2S04 in the solution is.

Hello, I can't see your diagram, and the problem can't be solved.

1. 2kmno4=k2mno4+mno2+o22g x=1g

Volume of oxygen v = mass density = 1 Do the math yourself.

2.3Fe + O2 = Fe3O2 (ferric dioxide) bottle burst is not put sand The temperature is too high, other asks.

The question is not easy to answer without a picture.

The B bottle is red, probably KMNO2 went inside.

(1) According to the figure, when 100g of sodium carbonate solution is added, it happens to be completely reacted, so when 200g of sodium carbonate solution is added, the sodium carbonate is excessive, and the resulting solution is a mixed solution, in which the solutes are NaCl and Na2CO3

2) Let the mass of calcium chloride in the sample be x, and the mass of sodium chloride generated is y CaCl2 + Na2CO3 = CaCO3 + 2NaClx 10g Y

111x=10010g=117y

The solution is x=, y=

Mass of sodium chloride in the sample =

The resulting solute mass fraction in solution =

Answer: The solute mass fraction in the obtained solution is 7% (other methods can be interpreted).

Please upload your diagram so that it can give you an answer. Saturated solution.

m =, the purity is 80%, and the mass fraction of hydrochloric acid is 7% Because the number given by the title clearly tells you that 10g of dilute hydrochloric acid is not enough to react with all limestone, what is reduced is the amount of carbon dioxide generated, every time 10g is added, the limestone will be reduced by 1g, and the last time 10g of dilute hydrochloric acid is added, because the amount of limestone is insufficient, so it is only reduced.

The last thing left is silica, so the purity is (

The mass fraction of hydrochloric acid is set to x, and the reaction between limestone and hydrochloric acid is CaCO3-2HCl, so, 100 73=1 10x, x=

ps: 100 is the molecular weight of limestone, and 73 is the molecular weight of hydrochloric acid*2

1) From the meaning of the title, it can be seen that the calcium carbonate is not consumed during the experiment, and the same amount of hydrochloric acid is added each time, and the mass of calcium carbonate consumed is equal, that is, m=2

2) As can be seen in the question, the reaction is sufficient, so after the fourth reaction, only silica remains in the solid.

Therefore, calcium carbonate purity w = (total mass of the sample - mass of the magazine) total mass of the sample = ((3) With the first two questions, it can be seen that there is a total of calcium carbonate in the sample, and the equation for the reaction of calcium carbonate and hydrochloric acid can be calculated to calculate the total mass of hydrochloric acid consumed m = (73*

i.e. mass fraction = m 40

(1) Speculate that the question they are going to study is:

What are the effects of neutral detergent solution and synthetic detergent solution and tap water on the growth of seeds?

2) You estimate that the results of Group B will be:

The seed dies. 3) The role of group C is to form a control group with group A and group B.

Analysis: [Conjectures and Hypotheses] If sodium hydroxide deteriorates, its product is sodium carbonate, so it can be combined with the conjectures in the question to complete the solution;

Experimental with **].

1) Sodium carbonate can react with dilute hydrochloric acid to form gas, while sodium hydroxide and dilute hydrochloric acid react without obvious phenomenon, and barium hydroxide solution reacts with sodium carbonate to form a white precipitate, which can be used to answer this question;

2) The sodium carbonate solution is alkaline, which can be phenolphthalein turning red, so in order to prevent sodium carbonate from interfering with the experiment, excessive barium chloride solution should be added, which can be answered accordingly;

3) According to the chemical equation of the reaction of barium chloride and sodium carbonate solution, the relationship between m and n can be obtained, and then the solution can be solved according to the information in the question;

Reflection] The deterioration of the sodium hydroxide solution is due to the reaction with carbon dioxide in the air to form sodium carbonate, and the chemical equation of the reaction can be written accordingly

Answer: Solution: [Conjecture and Hypothesis] If sodium hydroxide deteriorates, its product is sodium carbonate, and if sodium hydroxide is partially deteriorated, then the solid is a mixture of sodium hydroxide and sodium carbonate;

Experimental with **].

1) Sodium carbonate can react with dilute hydrochloric acid to form gas, so if there is no obvious phenomenon, there is no sodium carbonate in the solid, that is, only sodium hydroxide, that is, the conjecture is true;

The barium hydroxide solution reacts with sodium carbonate to produce white precipitated barium carbonate and sodium hydroxide, so if a white precipitate is observed, it means that sodium carbonate is contained in the solid, that is, the conjecture or conjecture is true; The chemical equation of this reaction is: Na2CO3 + Ba(OH)2 BaCO3 +2NaOh;

2) The sodium carbonate solution is alkaline and can be phenolphthalein turning red, so in order to prevent sodium carbonate from interfering with the experiment, the barium hydroxide solution in step 2 should be changed to add excess barium chloride solution;

3) Assuming that all the mg solids taken are sodium carbonate, then:

2naoh+co2=na2co3+h2o

Knowing the reason for this change will solve the problem.

Chemistry is not difficult, and careful analysis basically solves the problem.