Chemistry knowledge questions Big brother and sister who know how to help me

Summary. The maximum mass of oxygen produced is 32g, and the specific process is shown in the figure below.

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The maximum mass of oxygen produced is 32g, and the specific process is shown in the figure below.

Change the 136g in the process to 68g.

Chemical properties are intrinsic properties of matter (meaning that chemical properties determine the performance of chemical substances, it can be said that chemical properties are a general concept, and chemical substances are macroscopic objects composed of many microscopic particles).

It is the root cause of chemical changes.

Chemical change is the outward manifestation of the chemical properties of a substance.

Chemical properties are intrinsic (properties) of a substance and are the ones that undergo chemical changes (internal causes), whereas chemical changes are (manifestations) of the chemical properties of a substance.

Characteristics, internal causes, manifestations.

Attributes, internal causes, manifestations.

1. Phosphorus + oxygen - phosphorus pentoxide.

2. Magnesium + oxygen - magnesium oxide.

3. Hydrogen peroxide - manganese dioxide - > water + oxygen (manganese dioxide is the catalyst) 4. Potassium permanganate - heating - potassium > manganate + manganese dioxide + oxygen (the first two are talking about the clump solid doudan).

5. Iron + oxygen - ignition - > ferric tetroxide.

Chemical reaction Decomposition reaction: Contains cherry

When we chew the rice, it becomes sweet, and there is something called starch in the rice, which changes when it is chewed by the saliva.

Equation: 2(C6H10O5)N + H2O== (Salivary Amylase) ==NC12H22O11

Starch (2n pcs) + water = = (salivary amylase) = = maltose (n pcs).

The salivary amylase in saliva converts the starch in the steamed bread into sweet maltose.

Starch is converted into sugar by the action of salivary amylase, so it is a chemical reaction.

There is a lot of starch in steamed bread, and there is saliva in saliva, which is amylase. Chewing makes the steamed bread and saliva sink together, and the starch is catalyzed by enzymes to sucrose, maltose and other sweet substances.

Saliva contains saliva, which catalyzes the hydrolysis of starch in rice.

It's a chemical reaction, and the hydrolysis of the Bonai reaction results in a sweet hand of maltose.

So having a sweet taste when chewing rice is a chemical change.

Thinking about this question from the perspective of electrochemistry, A is the power supply, so there is a current flowing after the connection, no matter what pole B is, there should be a chemical reaction on C and D, according to the topic, C point is red, first of all, the red **, phenolphthalein test solution is red when it encounters alkaline substances, so the pH value of C point rises, that is, it becomes alkaline, which is caused by the electrolysis of sodium chloride solution to produce sodium hydroxide, then chlorine gas should be generated in D, chlorine gas is acidic in water, then the pH of D point decreases, so D will not be red. This has nothing to do with the electrode properties of C and D.

Red is the production of bases, that is, Cl- loses electrons to Cl2 and gets NaOH, so point C turns red, and point D produces HCl, which is not colored. The chemical reaction on the filter paper is carried out separately under the action of an external electric field, half of which is a reaction in which electrons are lost and half is a reaction in which electrons are gained. Half is an acid and half is a base, both because of the action of an applied electric field.

The addition of K2SO4 solution to C is equivalent to dilution with water, which slows down the reaction rate.

A. KCl solids do not participate in the reaction, but they do not change the concentration of the acid.

b. Since the acid is excessive, adding Fe powder will increase the amount of H2 generated.

D. The introduction of NO3- will make the presence of HNO3 in the solution, which will be reduced to NO by Zn, reducing the amount of H2.

SO42- is not actually involved in the reaction, and its concentration has nothing to do with the reaction rate.

Upstairs, what's the relationship between balance and speed?

Select C, add potassium sulfate to increase the concentration of sulfate in the system, thereby affecting the reaction balance of zinc and sulfuric acid and slowing down the reaction rate.

Answer the questions of other respondents: there are many factors that affect the rate of chemical reactions, reactant concentration, temperature, catalyst, etc., in terms of reactant concentration, increasing the concentration of reactants will speed up the reaction speed, on the contrary, increasing the concentration of products can slow down the reaction rate, in this question zinc reacts with sulfuric acid to form zinc sulfate, in the aqueous system it is dissociated into sulfate ions and zinc ions, adding potassium sulfate solution is to increase the concentration of sulfate, which is equivalent to increasing the concentration of products, thereby slowing down the reaction speed.

a. No impact.

b. The amount of hydrogen will increase, and the galvanic cell will be formed, which will increase the reaction speed c. Reduce the concentration of hydrogen ions, and the reaction speed will slow down.

d. There is nitric acid (hydrogen ions and nitrates) in the solution, and hydrogen gas is not generated. Choose C

c Potassium sulfate does not react with zinc, adding potassium sulfate solution essentially plays the role of diluting sulfuric acid solution, and the effect of adding water is almost drops, and the reaction rate is slowed down when sulfuric acid is diluted.

Compared with item a, potassium chloride does not react with zinc, but because it is a solid that does not play a role in dilution, the reaction rate remains unchanged.

Item B, due to the excess of sulfuric acid, after adding iron powder, iron reacts with sulfuric acid to form hydrogen, which increases the amount of hydrogen generated.

D, the difference between potassium nitrate solution and potassium sulfate is in the acid root. If hydrogen ions and nitrate ions exist at the same time in the solution, the solution will have strong oxidation, and the reaction will become Zn+Hno3=Zn(NO3)2+H2O+NOno Zinc will be consumed but no hydrogen will be generated.

In this question, sulfate ions do not participate in the reaction, and have nothing to do with sulfate ions, so they are not considered.