The chemistry master came in to help me, a senior year of chemistry

It has been pointed out in the literature that there are essentially two reactions in the solution of aluminum and sodium hydroxide: 2Al+6H2O(=)2Al(OH)3+3H2[4] Al(OH)3+NaOH=Naalo2+2H2O or expressed as: Al(OH)3+NaOH=NaAL(OH)4 The first reaction generates hydrogen, but the first reaction is very weak at room temperature, and it is difficult to escape from the surface of the aluminum sheet even if the gas is generated, and the gelatinous Al(OH) is generated at the same time 3. It may adhere to the surface of the aluminum sheet and prevent the reaction from proceeding.

Therefore, rather than explaining that the formation of hydrogen promotes the first reaction, it should be explained that the immediate dissolution of the generated Al(OH)3 affects the first reaction, prompting the reaction to proceed quickly and thoroughly. Fact.

In the second year of high school, you will know the principle of Le Châtea, although water and aluminum react slowly, but sodium hydroxide consumes the aluminum hydroxide produced, causing the equilibrium to move in a positive direction.

2al+6h2o=2al(0h)3+3h2 (the reaction is very weak at room temperature, that is, the reaction between Al and a strong base is still essentially a reaction with H+ in water).

al（oh）3+oh-===alo2- +2h2o

Although water and aluminum react slowly, sodium hydroxide consumes the resulting aluminum hydroxide, which reduces the aluminum hydroxide, and according to the Le Château principle, the equilibrium moves forward and the reaction can proceed.

Because it is alkaline, it contains a large amount of OH-

Mg(OH)2 and Agoh will precipitate while NH3H2O will volatilize, so Ag+, Mg+ and NH4+ cannot exist in large quantities.

HCO3- and OH- react to form CO3-, so there is no such choice C

b。Do you want to explain? HCO and OH do not coexist. MG and OH do not coexist. It should be. In fact, AG and OH do not coexist. And nh should be nh4.

What questions, how did not add.

Choose C. Conservation of electrons in redox reactions is utilized. Fluorine gains two electrons, so R loses two electrons.

After the valency of R rises by 2, one more oxygen is combined (from Ro3 to Ro4), so the oxygen in this reaction is negative 2 valence, so R in Ro3 is positive 6 valence. This kind of problem needs to infer the valency of oxygen, and those who directly calculate oxygen as a minus 2 valence are coincidentally correct. This kind of question often has the uncommon valency of the elements, which is a trap.

Nitrogen or fluorine? Is RO3 not charged?

Conservation according to charge. The right RO4- and 2F- have a total of 3 negative charges. The two hydroxides on the left have a total of 2 negative charges. Then RO3 has a negative charge of 1. So r is +5 and b

This is a redox reaction and follows the conservation of electrons. Now according to the equation, the valency change of r and f is judged, because f2 is converted to 2f-, two electrons are obtained, that is, the r element in the reactant ro3 loses two electrons and is converted into ro4, and the valency of r in ro4 is +X, SO THE VALENCY OF R IN RO3 is +(x-2).

ps: I feel that there seems to be a problem with your title, ro3 and ro4 should be negative ions, and you wrote fluorine.

There is a problem with the chemical equation that is not balanced.

The two gases can react with each other to form water under certain conditions, then these two gases are H2 and O2, Na and water react to form H2, Na2O2 and water react to form O2 so choose C

2. Chlorine water is produced by chlorine dissolving in water, and the reaction that occurs is Cl2 + H2O = HCl + HCl, which is an equilibrium reaction, and the concentration of each substance remains unchanged after reaching equilibrium.

This reaction occurs when left for a long time, 2HClo = HCl + O2 (the reaction is faster under photocatalysis).

As the HCl decreases, Cl2+H2O=HCl+HClO equilibrium proceeds to the right, and the HCl also increases, and the Cl ions increase.

It is placed in a sufficient amount of water to produce two gases, which in turn can react with each other to form water under certain conditions.

This sentence states that the two gases produced are H2 and O2

So Na reacts with water to form H2, Na2O2 reacts with water to form O2 equation: 4Na + 2H2O == 4NaOH + 2H2 (gas) 2Na2O2 + 2H2O == 4NaOH + O2 (gas) Saturated chlorine water reacts after being placed for a long time: 2HCl == 2HCl + O2 (gas) so HCl+ and Cl- are generated.

So choose C

The first gases generated are O2 and H2 and only two of C can produce both gases at the same time: Na2O2 and water to produce oxygen and Na and water to hydrogen.

The second product of Cl and water is HCl, which is unstable and decomposes, and only HCl is left, which is the Cl ion.

Affirmatively, Na202 should react with water to produce NaOH and 02, Na and water to form NaOH and H2, and hydrogen and oxygen to produce water. (Na2O reacts with water to produce only NaOH and no gas)

Question 2: It is the photolysis reaction of HCl, after HClL is placed for a long time, it will react with water to form HCL and 02, oxygen escapes, and Cl ions increase.

The two gases, in turn, can react with each other to form water under certain conditions.

It proves that there are h2 and o2

You can generate H2 only Na.

There is also a person who can produce O2 in water, showing that Na2O2 Cl water will react with water, Cl2+H20=HCl+HCl, or reversible, the reaction time is longer, 2HCl=2HCl+02 (gas), so there are more Cl ions.

Sodium peroxide is combined with water to produce oxygen.

Sodium is combined with water to produce hydrogen.

Hydrogen and oxygen can react to form water.

Chlorinated water turns into hydrochloric acid and hypochlorous acid.

Because plasma TVs are more popular.

Concentrated ammonia is alkaline, volatile, volatile ammonia contact with the water on the paper and becomes ammonia, alkaline, in this way, the butterfly turns red. Concentrated sulfuric acid is not volatile. So d no.

b Concentrated ammonia is formed by the alkaline gas NH3 dissolved in water, which is alkaline, while phenolphthalein turns red when exposed to alkaline solution, and does not change color when exposed to acidic solution, excluding A, and B is correct; c, sodium hydroxide solution will make litmus solution blue; Concentrated sulfuric acid will turn the litmus solution red. To sum up, only option b is correct.

PS: Ammonia is a common alkali, and it is a weak alkali, but it has the general properties of alkali.

Pick B (concentrated ammonia is, of course, alkali!) Concentrated ammonia is volatile, and phenolphthalein turns red.

Option B Only when the liquid volatilizes on the paper, the two items will react when they come into contact, so C and D are excluded. However, hydrochloric acid cannot make the phthalein red, and the concentrated ammonia is strong enough to make the phthalein red.

Select b Concentrated ammonia is alkali.

Item A acid and phenolphthalein have no chromogenic reaction.

Item B base and phenolphthalein appear red.

The c-item base and litmus are blue.

Item D concentrated sulfuric acid is non-volatile and cannot be colored.

A and B, concentrated hydrochloric acid and concentrated ammonia are volatile, if reagent A is colorless, then it can only be B answer, if reagent A is not told in the figure, then both A and B can be selected.

b. Concentrated ammonia alkaline gas dissolved in water.

c.Litmus solution Sodium hydroxide solution base.

b.Don't ask me why, just remember.

Don't think too complicated about this topic, the idea is like this.

The first letter learned that the world knew that the ionization constant of a certain acid must be certain, and the stronger the acid, the greater the k.

1.Why can't water distinguish between their acidity?

Because the ability of water to ionize H+ is weak, and there is very little H+ in water, the so-called acidity is to compare the degree of ionization, right? Slippery limbs.

If there is less H+ in the water, the total H+ will be less, and the H+ will come out of the acid according to the ionization balance.

Everyone has a lot of land liquid, and it is impossible to compare.

If acid is used, there is H+ in it, and then consider the ionization balance, there is more H+, and the acid balance that could have been completely ionized is disturbed, and it cannot be completely ionized, and the ionization ability is different, the proportion of acid ionization is different, and the acidity is compared.

So choose one that is more acidic than water, A, it seems to be a neutral substance (from high school), I haven't heard that there is H+ in it, C is a base, and D has the same chemical properties as water.

This is a concept of leveling effect and discriminating effect.

for strong acids in aqueous solution.

The ability to give protons is very strong, and the alkalinity of water is enough to accept the protons given by these acids, as long as the concentration of these acids is not too large, then they will react with water quantitatively and convert all into H3O+, that is, HCO4+H2O H3O++ClO4-, etc.

That is, all of their acidic ground intensity is flattened to the level of H3O+, and this effect of leveling different strengths of acids to the level of solvated protons (in this case, hydrated protons H3O+) is called the leveling effect.

The strength of the above four acids in aqueous solution is equal, but in glacial acetic acid, their strength is different, which can be distinguished by glacial acetic acid.

hclo4+hac--h2ac++clo4-

ka=h2so4+hac---h2ac++hso4-

ka=hcl+hac---h2ac++cl-

ka=hno3+hac---h2ac++no3-

Ka = Therefore, glacial acetic acid is the distinguishing solvent of the above four acids.