Chemistry Olympiad Pointing at the high fingers, the Chemistry Olympiad questions are mastered

I have participated in the Sichuan Provincial Olympiad, the general process of the Olympiad is to first compete at the municipal level, and then participate in the provincial competition in the province after obtaining the ranking, and if you also pass, you will participate in the national competition, and if you are the first in the national competition, you can be directly admitted to a prestigious school, and at the same time, you can represent the country to participate in the Asian level, and even the world

Now that you are in your first year of high school, you can ask your chemistry teacher when you will sign up, and if you want to participate in the Olympiad, you can only participate in the first and second years of high school, and there is no time for the third year of high school (unless you tutor).

As for having knowledge, it is possible to meet but not to seek, to see more extracurricular knowledge in chemistry, you must read all the books in the second and third years of high school by yourself in the first year of high school, and you must understand all (the books are basic, you must understand, and if you understand, you may not necessarily pass) read more books of the Olympiad, inorganic matter to look at copper elements and 4th cycle elements, organic matter to see cyclic hydrocarbons and aromatic alkanes and their derivatives! (You can see the inorganic chemistry textbooks at the university).

Awards, provincial first prizes and national first and second prizes will be added to the total score of the college entrance examination.

I am now in my first year of high school in Tianjin, and our school now has the Olympiad of Mathematics, Physics and Chemistry, but I have to take the exam, although I am admitted but I don't want to go to the ball, after all, the competition pressure in Tianjin is too great, and it is too risky to specialize in one subject all the time. As for the book... It is the best that suits oneself and sticks it into the textbook.

This is the 2007 Bengbu No. 2 Middle School Experimental Class Enrollment Paper, right? Hehe, this is the 2007 Bengbu No. 2 Middle School Experimental Class Enrollment Paper, right? Huh 1The solution that can make phenolphthalein reddened contains a large amount of HCO3- of OH-,A that reacts with OH-

hco3-oh-

co32-h2o;

Cu2+ in C reacts with OH-

cu2+2oh-

cu(oh)2;

Fe3+ reacts with OH- in D:

fe3+3oh-

Fe(OH)3, so choose B

2.Let the alloys be magnesium, then hydrogen mass =

Assuming that the alloys are all aluminum, then the mass of hydrogen = is generated, and the actual result should be somewhere in between.

Therefore, C. is chosenThis question is not qualified enough to be quantitatively calculated, and the answer can only be selected by considering the limit results.

fecl2h2,fe2o3

6hcl2fecl3

3h2o,fe3o4

8hclfecl2

2fecl3

4h2o,naoh

hclnacl

H2O, so choose B

The Chemistry Race (Inorganic) consists of two parts: elemental chemistry and basic theory.

The key and difficult points of the chemistry competition are also often tested (preliminary round) mainly complexes, crystal structure description and judgment, most of which are qualitative, hybrid orbitals will not be directly examined, it is useful to draw molecular configurations and explain some special phenomena, and other grips are similar and compatible, and there will be calculations of equilibrium constants this year, and then there are titrations and unknown compound judgments, which require rich knowledge of the properties of special compounds, redox and battery principles (positive and negative electrodes, essence) Don't make a fool of the wrong guess, almost.

In terms of organic, because it is the natural growth point of the textbook, all the chapters about hydrocarbons in the university book should be read carefully, find some rules, back reactions, naming and the properties of each functional group to figure out, and memorize some of the key signature reactions of the compound and the reactions commonly used in synthesis (such as the growth and shortening of carbon chains) to the derivatives, the focus should be on finding the rules, because many of the reactions in the exam questions can be said to be made up, relying on "guessing", but only the most solid basic skills can guess correctly...

Let's assume that a certain number of molecules have a volume of 1a

2co+o2=2co2

Because the ratio of the number of molecules is equal to the volume ratio, the product 2a and the reactant 3a, i.e., 1ml = 1a

There are 2 scenarios to consider below:

1.The first time (closed ignition) the O2 is completely depleted, the oxygen volume is that 1ml

Because NAOH only absorbs CO2, because it is reduced by 5ml, the current CO25ml, deducting the generated 2ml, is the original 3ml

8ml-5ml = 3ml, because O2 is depleted, so the remaining 3ml after this through sodium hydroxide is all CO, plus the first ignition.

The 2ml consumed is 5ml, so the ratio is 3:1:5

When it is completely depleted, the volume of carbon monoxide is 2ml

Because NAOH only absorbs CO2, because it is reduced by 5ml, the current CO25ml, deducting the generated 2ml, is the original 3ml

8ml-5ml=3ml, because the CO is exhausted, the remaining 3ml after passing through the sodium hydroxide is all O2, plus the first ignition.

The 1ml consumed is 4ml, so the ratio is 3:4:2

Let the original gas mixture CO2 be XML

Consumption of 5 ml by NaOH indicates that 5-xml of CO22CO+O2=2CO2 was generated

X+(5-X) 2+5-x=9-3 gives X=3When O2 is excessive: (5-3) 2+3=4ml, then the volume ratio of CO=2ml is: 3:4:2

When CO is excessive: 5-3+3=5ml, then the volume ratio of O2=1ml is: 3:1:5

There are 3 electrons in the outer shell of Ca, forming +3 valence ions, and B is molded into compound A2B3, indicating that B is -2 valence, if B can have the highest positive valence, hunger is +6 valence, so B corresponds to the most ** oxidation code stupid hydrate in the +6 valence, that is.

C, Explanation: There are 3 electrons in the outermost shell of the atom of element A, and the valency of A in the A2B3 chemical complex is +3, then the valency of the pure imitation of B is -2, and the outermost shell of the B atom has 6 electrons. The most ** is +6, c meets the requirements, answer c

C is chosen because A has an electron in the outermost shell and the compound is.

A2B3, then the orange in the compound A loses 3 electrons and is buried in the bull electricity, so the compound A2B3 in A shows a positive 3 valence, that is, B shows a negative 2 valence. And because Wu fiber is the absolute value of the lowest price of the element, it is the highest in B.

Valence compounds. The price state is plus 6 price!

Hello landlord! Let's choose C!

A is aluminum, b is sulfur, and the hydrate of the most ** oxide is the chemical formula of the closed potato in the state is: sulfuric acid bar. h2so4

I hope it can help you

Start by writing the reaction:

a) Cu + H2SO4 = (heating) = CuSO4 + H2 (Cu complete reaction).

n 10/64 10/64 10/64

m 10（g）

Iron replaces copper, the mass remains unchanged, indicating that iron reacts before sulfuric acid, let m=a+b, a is the mass that completely reacts with sulfuric acid, and b is the mass of copper replacement.

b) Fe + H2SO4 = FeSO4 + H2 (H2SO4 complete reaction).

n a/56 a/56

m a（g）

Replacement of iron and copper:

c) Fe + CuSO4 = FeSO4 + Cu (Fe complete reaction).

n b/56 b/56

m b（g） b/56*64=m-b（g）

In nitric oxide, a bond is formed between nitrogen and oxygen, a 2-electron bond, and a 3-electron bond.

The bond between nitrogen and oxygen is that nitrogen and oxygen each have a lone pair of electrons.

With 11 valence electrons, it is an odd electron molecule and is paramagnetic.

Molecular orbital formula: (1s)2(1s*)2(2s)2(2s*)2(2p)2(2p)4(2p*)1

If you have to say how many unpaired electrons there are, it's only 1 electron on 2p*.

Suitable for high school chemistry competitions. Please ignore the college entrance examination.