Solve high school chemistry problems, solve high school chemistry problems

Let's discuss it in the following cases:

If all the solutes are dissolved in water and there is no chemical reaction with water, the calculation is calculated directly using (solute mass solution mass)*100%.

If the solute does not react with water, but is not fully dissolved, the solute mass is only calculated as the dissolved part, and the undissolved part cannot be included in the calculation.

If the solute reacts with water when it is dissolved in water, the solute in the solution is the product of the reaction.

If the solute is a crystalline hydrate, after being dissolved in water, the mass of the solute does not include the mass of the crystalline water. Because when the crystal hydrate is dissolved in water, the crystal water is converted into a solvent in solution.

You can check out the encyclopedia for detailed answers.

In general, it is the product, i.e. sodium hydroxide.

However, with some exceptions, such as the solute of ammonia, is counted as NH3.

This is to figure out the properties of the solution. The solution is a stable system and there is no reaction between the solute and the solvent. If sodium is a solute, it will react with solvents, which is not true.

Therefore, the concentration should be calculated only after all the reactions have been completed, and the rest is the same reason. The ammonia mentioned upstairs is very special, mainly because the concentration of ammonia monohydrate is too small and can be ignored, most of it is ammonia, so it is calculated by ammonia.

Calculated after the reaction. After sodium reacts with water, the solute is sodium hydroxide instead of sodium, so the mass of sodium hydroxide is the mass of the solute.

It is clear that the reaction in this question is based on the displacement reaction of zinc and copper sulphate to form the galvanic cell. Let me explain in detail the flow direction of electrons.

First of all, zinc will lose electrons and transfer to the A-terminal, and then the hydrogen ions ionized by the water on the filter paper will get electrons, and the hydroxide will move to the B-terminal due to repulsion, and the hydroxide at the B-terminal will lose electrons and pass to the copper ions, and the hydrogen ions produced will move to the A-terminal, that is to say, the filter paper is an electrolytic cell with sodium sulfate as the electrolyte.

a.It is not stated which electrode it is, error.

b.That's right. c.Because of the existence of the salt bridge, it should be that the concentration of chloride ions increases, and the hydroxide at the wrong end participates in the reaction and only hydrogen ions remain, which is acidic and wrong.

Filter paper soaked with a saturated sodium sulfate solution is equivalent to a conductive solution system, i.e. a resistor where the current is converted into chemical and thermal energy by doing work.

In this way, the whole is still a galvanic battery! It is important to note that the transfer of current can only be achieved in the form of electron movement in metal electrodes and metal wires, and in electrolyte-containing solutions, the transfer of current depends on the movement of anions and cations in the solution. Throughout the circuit, the current is uninterrupted.

Hope to solve your doubts.

This galvanic cell is equivalent to Zn in copper sulfate solution, which can be spontaneous, Zn loses electrons, and Cu electrons are generally active metals as negative electrodes in the galvanic cells.

This reaction is spontaneous.

zn＋cuso4=znso4＋cu

Let nxoy, then nxoy+yh2=x 2n2+yh2o let h2 react ymol, so 2y-x=4 x=2, y=3 or x=4, y=4 or x=6, y=5 or x=8, y=6 can only be x=2, y=3, i.e., n2o3

a.It may be that blinking an eye will cause the acid to melt into it (my understanding) b, the concentrated alkali solution should be neutralized with the acid, but the strong acid will damage the hand.

c.Add water first, and concentrated sulfuric acid will splash.

d.Alcohol dissolves in water and burns in water.

Gasoline and sodium chloride solution are incommiscible, ethanol and water are soluble but have different boiling points, sodium chloride and elemental bromine are soluble in water, so they cannot be distilled with separate liquids.

It is useless to rinse with the solution to be configured, because the volumetric flask is to prepare the solution, and the configured solution should be imported into it, and the volumetric flask should be shaken well during operation, so a

At room temperature, a dense oxide film will be formed, and the oxide film will prevent it from continuing to oxidize.

If it is a, it means that there is no metal left.

Aluminium hydroxide can condense suspended solids in water and adsorb pigments.

Silicon has a high melting point and is inexpensive.

The reaction equation is SO2 + Cl2 + 2H2O = H2SO4 + 2HCl

A: It should be rinsed with water immediately.

C: Graduated cylinders cannot be used to prepare solutions.

D: When the alcohol is burning on the test bench, cover the flame with a rag.

Gasoline and sodium chloride solutions are not miscible with each other.

39 percent ethanol solution The two are miscible in the two.

Sodium chloride solution and aqueous solution of elemental bromine, both soluble in water, but bromine is more soluble in organic solvents, and washing with the solution to be configured will lead to an increase in the mass fraction of the solute, and the aluminum sheet can be placed in an unsealed carton for a long time, and the aluminum sheet will not form a dense oxide film at room temperature, which prevents the further reaction of aluminum.

The remaining solids can be attracted to magnets after filtration, indicating that there is iron formation, so there are fewer ferrous ions in the solution.

The energy of the photons is transferred to the silicon atoms, so that the electrons undergo a migration, and the free electrons accumulate to form a potential difference, when the external circuit is turned on, under the action of this voltage, there will be a current flowing through the external circuit to produce a certain output power. The essence of this process is: the process of converting photon energy into electrical energy;

so2+cl2+2h2o=2hcl+h2so4！！

“c.Adding water first and concentrated sulfuric acid will splash "The top floor is wrong, the order is correct, but the graduated cylinder can't prepare the solution!" The application of silicon should be mainly for semiconductors.

A This can only be said to be experience, and it is obviously wrong, if it is concentrated sulfuric acid, washing with water will release heat and cause more damage.

b This is the original language of the textbook, and the words have not changed.

cThis is equivalent to acid into water, which will release a large amount of exothermic and moist acid splashes.

d needs to be extinguished with a damp rag, which is also the original words in the book.

Gasoline and NaClaq are immiscible and separated. Ethanol and water are miscible in infinite proportions and can only be distilled (by the way, a water absorbent can also be used). Naclaq and elemental bromine are immiscible (liquid bromine is denser than water but will form bromine water due to diffusion), extraction.

Option b will make the concentration of the prepared solution too large (the correct operation textbook is available, very detailed).

AL generates a dense oxide film in the air to protect the internal metal from further corrosion and is not sealed for storage.

It can be attracted by the magnet, indicating that there is elemental iron remaining, and the ionic order of the reaction of elemental iron in the mixed solution is that the trivalent iron is greater than the divalent copper ion, and the hydrogen ion is more than the divalent copper ion, and the divalent copper ion is all replaced by elemental matter, and there are only divalent iron ions in the solution.

Aluminum hydroxide is a colloidal substance that can adsorb suspended solids and pigments, and should be the definition of the textbook. (Otherwise, you can only remember).

The composition of sand is silica, so silicon is widely used, and the raw materials are cheap (desert or something) or there is elemental silicon that can better absorb the sun's energy and convert it into electricity.

Sulfur dioxide and chlorine react to form sulfuric acid and hydrochloric acid, which are non-bleaching.

Anyway, classmates, go back and read the book, a lot of it is the content of the book, remember to give points

Conservation of charge means that the total charge number of anion and cation in the solution is the same, that is, the solution is electrically neutral.

The trick is to see how many anions and cations there are.

The main method of extinguishing the fire is to isolate oxygen or combustibles, because alcohol can burn, so choose to isolate oxygen, generally you can soak the rag with water to cover the fire area.

It is possible that the modified substance is chlorine absorption, and sulfur dioxide is bleaching in a magenta solution.

There are a lot of problems, the first option a is the treatment of acid to **, it is difficult to say what is specific in the eyes, and the measuring bucket can not be prepared with solution, water and alcohol can be miscible in any ratio, and water cannot extinguish the fire of alcohol.

The second question, your answer is correct.

When the third volumetric flask is used to prepare the solution, the accuracy of the solution that is mixed after being washed with the liquid to be prepared cannot meet the requirements.

After aluminum generates a dense oxide film, it can protect the central part from oxidation, which is equivalent to a protective film on the outer layer, so it is feasible.

The fifth can be attracted by the magnet to prove that there is iron left, so the reaction is complete, and the iron can replace the copper chloride, so there are no copper ions left in the solution.

The sixth aluminium hydroxide is adsorbent and was originally used to purify water to remove sediment and some pigments.

Solar cells are invented using the principle of photoelectric conversion, which requires a special structure formed by semiconductors to be realized, and silicon as a semiconductor element has become a common material for manufacturing solar cells with its advantages in terms of content.

The last possibility is that the colored substance cannot be oxidized by these two gases, so it does not fade.

It's easy to make this kind of question with a three-stage format.

Start by writing the equation 2SO2 + O2 *****= 2SO3

The amount of substance at the beginning is 0

The amount of the substance that varies 2x x 2x

The amount of matter at the end of 4s is 2x

Then there is x=

So δN(O2)=

v(o2)=δn(o2)/(v*t)=

The solubility of sodium bicarbonate is less than that of sodium carbonate when the temperature of Na2CO3 + H2O + CO2 = 2HCO3 is the same when the temperature of Na2CO3 + H2O + CO2 = = 2HCO3 is the same temperature of water.

The introduction of carbon dioxide into the already saturated sodium carbonate solution will cause the relatively stable Na2CO3 and CO2 to react with the H2O in the solution to precipitate NaHCO3

A reaction will occur:

co32- +co2 + h2o = 2hco3-

The solubility of NaHCO3 is less than that of Na2CO3.

From (1) to (2), the increment of the amount of matter of no is: (then from no3- to no, from (1) to (2) the electron transfer increment is:

From the conservation of electrons, from (1) to (2), if one of the compounds in the filter residue is a divalent metal, then its atomic weight is: (, then the metal is fe, then the ionic equation that occurs in (1) is as follows:

3Fe+ +2NO3- +8H+ = 3Fe2+ +2NO+4H2OIn the same way, from (2) to (3), if one of the compounds in the filter residue is a divalent metal, then its atomic weight is: (, then the metal is Cu

When (3) to (4), then the following ionic equation occurs:

3Fe2+ +NO3- +2H+ = 3Fe3+ +NO+H2O, then the gas volume increment is: liters.

Then v = liter.

In experiment 1, the chemical formula of the reflected ion is 3Fe+8H+ +2NO3-=3Fe2+ +2NO+4H2O, and V=in Reaction 4; The reason is as follows: because it is a mixture of iron contract, it first reacts with dilute nitric acid to form divalent iron and carbon monoxide, and after the iron reaction is complete, then the reaction between copper and dilute nitric acid produces divalent copper and NO, that is, the copper begins to react in the third step, and the reaction is complete at one time. The final step is the oxidation of ferric iron to ferric iron, and at the same time the formation of carbon monoxide, and you should be able to write the specific equation.

The basis for judgment is: after reaction two, the remaining solid is, just a multiple of the relative molecular mass of copper, and then it can be inferred.

3cu+8h+＋2no3-＝3cu2+＋2no↑＋4h2o2.From the experiment, it can be seen that the amount of nitric acid is n(hno3)=4n(no)=4 (c(hno3)=

The experiment consumes metals, all Fe, which is exactly in line with the above reaction, and the experiments consume metals that are also Fe, and the rest is Cu, which also coincides with the above reaction.

So in the mixture n(fe)= , the experimental metal just reacts completely, and the experimental is actually Fe2+ reacting with Hno3.

3Fe2+ 4H+ NO3- 3Fe3+ NO2H2O Fe2+ reacts exactly completely with NO, and the volume of NO is V=

Because the reaction is carried out in two steps, first aluminum and water react to form aluminum hydroxide and hydrogen gas, and the resulting aluminum hydroxide reacts with sodium hydroxide. The reaction equation is as follows:

(1) The solution of aluminum and sodium hydroxide is a two-step reaction!

2)2ai + 6h2o == 2ai(oh)3 + 3h2(3)2ai(oh)3 + 2naoh == 2naaio2 + 4h2o

4) Two-formula merge!

2ai + 2naoh + 2h2o == 2naaio2 + 3h2

Two different reaction mechanisms. The reaction with sodium hydroxide is divided into two steps, and aluminum hydroxide is formed, and then aluminum hydroxide and sodium hydroxide are formed into sodium metaaluminate. The reaction with the acid is the reaction of the pure metal with the acid.

Aluminum and sodium hydroxide are added with water to produce sodium metaaluminate and hydrogen.

But hydrochloric acid and aluminum are aluminum chloride and hydrogen.

These two are not reactions of the same nature.

Either nacn na2co3 ch3coonah2co3 ka2= or kach3cooh ka= of hco3-

We see. The acidity is CH3COOH HCN HCO3-

The larger the ka, the more acidic it is.

Then the alkalinity is just reversed.

na2co3＞nacn＞ch3coona