High School Chemistry, Explained, High School Chemistry Please explain

HA may be weakly acidic, weakly ionized, pH greater than or equal to 7

(1) CaCl2 +H2O2 +2NH3 +8H2O== precipitation) +2NH4Cl

2) Take an appropriate amount of the last washing solution, add nitric acid acidified silver nitrate solution, if there is a white precipitate, it proves that it is not clean; Otherwise, it is qualified.

3) At this temperature, the reaction of generating calcium peroxide octahydrate is prone to occur At low temperature, the generated calcium peroxide octahydrate is stable and not easy to decompose.

4) Relational:

n is obtained by n=, so m=, then the mass fraction is low.

a.According to our knowledge in the elementary school years, the atom is most stable when it reaches the structure of a noble gas. Therefore, P can also bind 2 Cl to form PCL5Therefore a error.

b correct. P and N are homogeneous elements, and the structure of Pcl3 can be referred to ammonia.

c error. There are 5 p-cl bonds in the phosphorus pentachloride molecule. This one has a structure diagram in the book trigonal bipyramidal structure.

d correct. 3s indicates that the s orbital already has pairs of electrons, and if it is really not needed according to the traditional theory of addition and subtraction, it can no longer be bonded.

Therefore, the theory of valence electron repulsion was born, and the formation of phosphorus pentachloride was well explained.

4) Acetate becomes CO2. Oxygenation and dehydrogenation are oxidation reactions that lose electrons. In galvanic cells, one of the electrons lost is negative.

5) Looking at the figure, at the A pole (positive pole), after the reaction of p-chlorophenol, it becomes cl- and phenol. It is equivalent to breaking off the chlorine atom and connecting the fracture with an H. The title says that under acidic conditions, that is to say, there is a large amount of H+, and now the material of H atoms is enough, and there is still a shortage of electrons, electrons**?

It is given by the acetate of the B pole.

6) According to the reaction of 5, it can be seen that 2 electrons consume one h+. I'm surprised, there's something wrong with this question! A polar region consumes H+, and the pH is going to rise, how can it be reduced from 4 to 1. It is estimated that it is reversed, and it is almost the same from 1 to 4.

H+= consumed. Then the electron obtained is.

How many electrons can I lose by breaking down an acetate? According to the hydrogen-oxygen price method, the o is -4 valence, and there is a negative charge -1 valence. 3 Hs is +1 valence.

Now the negative valence is -4, the positive valence is +3, and it also carries a negative charge.

So, the 2 C's are 0 prices. It becomes CO2 and is +4 valence. Lose 4e.

2 C's lose 8e.

So the decomposition of acetate:. Then sodium acetate is also so much.

Convert to mass. The molecular weight of sodium acetate is 82

Then the mass of sodium acetate is 82

Reaction 1 is to dissolve Al and Al2O3 and then filter, there are Al3+ and Na+, Oh- in the solution

The purpose of reaction 2 is to remove Na+ and OH- by filtrate. And leave Al in the precipitate, i.e. aluminum hydroxide.

Reaction 3 is the formation of aluminum nitrate with dilute nitric acid.

In this way, the amount of dilute nitric acid should be controlled in reaction 2, and if the dilute nitric acid is excessive, the aluminum hydroxide precipitate will dissolve into the solution and be removed along with Na+ and OH-.

Excessive carbon dioxide was used to reduce the pH value of the filtrate after reaction 1, so that it was close to 7, and the solubility product of aluminum hydroxide in neutral and weak alkaline environments was very small.

Vacuum evaporation is also to be heated, but the boiling point is reduced under pressure. The aluminum nitrate solution is heated, and the heating promotes hydrolysis.

The hydrolysate has nitric acid, but nitric acid is a volatile acid, and part of the nitric acid will overflow the reaction system in the form of gas during the evaporation process.

The hydrolysis reaction proceeds in the forward direction, Al(NO3)3+H2O=reversible=Al(OH)3+Hno3 gas.

Al(NO3)3 is heated to generate 2 gases, the valency of AL does not change, the thermal decomposition regularity of solid metal nitrate (NO3-), NO3- self-redox reaction, and there must be oxygen generation, and the other is an oxide of N.

4:1 volume, say O2 is 1 volume, O-2 valence, 2 O-2 valence - 2 O0 valence is to lose 2x2 = 4 electrons, 4 volume is N oxide to get 4 electrons (electron gain and loss is conserved) that is, No2 (4 N + 5 - 4 N + 4).

5. The temperature of water vapor is high, so the introduction of water vapor must make the reaction system warm up and accelerate the reaction.

In addition, the introduced gas has a disturbing effect on the reaction system, so that the product is effectively separated from the surface of the reactant and the reaction rate is accelerated.

2Al+2OH—+2H2O 2ALO2—+3H2 (or Al2O3 + 2OH— 2ALO2— +H2O).

How to control the end point of the reaction (or the amount of nitric acid) Replace the addition of dilute nitric acid with the introduction of excess CO2 to prevent the hydrolysis of aluminum nitrate.

4Al(NO3)3 2AL2O3 12NO2 3O2 Increase the temperature and stir to accelerate the reaction rate.

Indicates the absence of ferric ions.

Let's look at this gas first, it is colorless and turns reddish-brown when exposed to air. In secondary school, reddish-brown gas is NO2.

Therefore, the emitted gas is NO, and it reacts with the air to form NO2, so it is judged to have nitrate.

The nitrate group becomes no from +5 valence electrons, so there must be a reducing agent to lose electrons to him, and the only one that can be oxidized by nitrate is Fe2+

There is also information that after the addition of hydrochloric acid, the anion type does not change, and if there are no chloride ions in itself, the anion type will change when hydrochloric acid (containing chloride ions) is added. Therefore, judging that the analysis of the building was very good, there was a small mistake here, hehe. Expressing regret.

Now the identified ones are Fe2+, NO3-, Cl-Now there are 5 ions, and 3 ions have been identified.

According to the conservation of charge, 1 mol of ferrous ions, followed by 1 mol of nitrate and 1 mol of chloride. It happens that the positive and negative charges are equal.

So the problem is changed here to this: the remaining two ions must be one yin and one yang. And the two charges are positive and negative.

Ferrous ions and OH- cannot coexist, so OH- is excluded, and the remaining alternatives are: CO3 2-, SO4 2-, sodium ions, aluminum ions, magnesium ions.

It is known that each ion is 1mol, and aluminum ions can be directly excluded. Sodium ions.

Because both carbonate and sulfate are -2 valent, they should be combined with the amount of other substances to form a compound, and the charge is equal to positive and negative. There must be a +2 valence cation. +3, +1 price of aluminum, sodium can not be satisfied.

So this cation is magnesium ion, then the anion must be sulfate. Why? Why, you ask? Magnesium carbonate is precipitation! Although the title says that hydrolysis is not considered, it does not say that precipitation is not considered.

At this point in the analysis, there is nothing to say. The hardest thing is the first empty. The second empty writes by yourself.

Thirdly, a sufficient amount of sodium hydroxide is added to form a precipitation of ferrous hydroxide and magnesium hydroxide. What is obtained after burning is not ferrous oxide! Here's another pit!

That's the way chemistry is the problem, you didn't negotiate the pit. Ferrous hydroxide is present in solution for a while and is oxidized to iron hydroxide. Coupled with the process of evaporative heating, it will be converted into iron hydroxide.

According to the law of conservation of mass, the final result is ferric oxide, and 1mol of magnesium oxide.

2cu2s + 14hno3 ==2 cu(no3)2 +2cuso4 +5no.+ 5no2 + 7h2o

The number of transferred electrons is Lu Sheng, and the old silver is constant, and the elements are conserved.

1) There is nothing to say about this, but it is the writing of ion equations. Ammonia is written in the ionic equation in the form of ammonia monohydrate. Nothing else. 4nh3·h2o+cuso4==[cu(nh3)4]so4+4h2o

2) The orbital formula of the ground state n atom is also nothing to say: 1s22s22p3

There's nothing to say about this, just pay attention to the traps, it's the metal cation that asks you, and the ammonium ion is not a metal cation. To put it bluntly, let you write the electronic configuration of cuprous ions, copper is the 29th element.

29 2 8 18 This is the electronic configuration of cuprous ions. Draw a circle in the middle, and arcs in 2, 8, and 18.

3) Sulfate is a tetrahedral structure. Sulfur atom sp3 hybridization. Then the bond angle of all tetrahedron is 109 degrees 28 minutes. This is common sense, just remember it.

In NH3, the electronegativity of the N element is much stronger than that of H, and the electron cloud is biased towards N, so the lone pair of electrons of N is more convex and easy to form ligands.

In NF3, the electronegativity of F is much stronger than N, and the electron cloud is biased towards F, resulting in the lone pair of electrons of N not convex, and it is difficult to form ligands.

If there is only such a point, then write f with strong electronegativity.

4）o-h…n,o-h…o,n-h…n

In ammonia, there are three types of hydrogen bonds between water and water, ammonia and water, and ammonia and ammonia.

5) The number of copper atoms contained in this unit cell, as mentioned last time. 1 8 for vertices, 1 2 for faces

Therefore it is 8 1 8 + 6 1 2 = 1 + 3 = 4.

The relative atomic weight of copper is m. Its molar mass is m gram mol

That is, the mass of 1mol of copper is m grams, and 1mol has na copper atoms. That is, the mass of na copper atoms is m grams.

Then the mass of each copper atom is m na grams.

Now there are 4 copper atoms in this unit cell. Then the mass of the unit cell is 4M Na.

The volume of the unit cell. It's AB. ab=bc。

In RT ABC, the length of AB can be solved directly using the Pythagorean theorem: AC = 2AB. AC=4D Equivalent Substitution:

16d²=2ab²。Solution: ab=2 2d

The volume of the unit cell is 16 2d

Hence the density of the crystal = the mass of the crystal: the volume of the crystal.

4m (16 2d na) after approximation: m (4 2d na).

（1）cu2+ +4nh3*h2o=[cu(nh3)4]2+ +4h2o

2) Draw an up arrow inside each of the three boxes, and finally write 2p [ar]3d10 on the top

3) The bond angle of tetrahedral s02 is slightly less than 120°, so it should not be necessary to know the specific value.

SP3 Reason (not sure): The relative molecular mass of NF3 is greater than NH3, which is more stable and less likely to form ligand ions with copper ions.

4) Can't draw ......

5) From ( ) can be obtained the volume of (2 root number 2d) to the 3rd power, there are 4 atoms in a copper unit cell, so the mass is 4m na, in summary: the density is the root number 2m 8nad (Jiangsu college entrance examination does not test this, so the answer does not know whether it is right or not......）

In C A, the gaseous state of the shirt grinding becomes liquid, the density increases, and the entropy decreases or stops; In b, S is greater than 0 and h is greater than 0, and You Jing can react at high temperature; d is a reversible reaction and cannot be completely converted, and k is never equal to 20.