I would like to ask questions about chemistry in the third year of junior high school, and a few que

First of all, the ZN insertion filtrate is bubble-free, acid-free, and a mistake. Dilute sulfuric acid can react with copper oxide and iron, and it is possible that it reacts with both iron and copper oxide, so the cd term is written"There must be"If they are all wrong, then the b is correct. No matter who reacts with dilute sulfuric acid first, iron ions are more active than copper ions, so there must be ferrous sulfate.

There is no reaction when adding zinc sheets, indicating that the sulfuric acid has been consumed, according to the metal activity order table, copper is behind iron, so sulfuric acid will first react with copper oxide to form copper sulfate, and then iron and copper sulfate will undergo a displacement reaction to form ferrous sulfate.

If all of it is copper oxide, it will react with sulfuric acid to form blue copper sulfate, and if you put it in a zinc sheet, zinc will replace all the copper before reacting with the excess acid.

There is a mixture of iron and copper oxide, so there is copper only after all the iron is dissolved.

Even if the sulfuric acid reacts with copper oxide first, iron will displace the copper ions.

If you choose the wrong BA, the zinc sheet is inserted into the filtrate without gas, indicating that it does not contain acid.

c The filter paper does not necessarily contain copper oxide, and it can be fully reflected.

D is wrong, and the principle is the same as C.

There must be ferrous sulfate in b, iron reacts with sulfuric acid to form ferrous sulfate, and copper oxide reacts to form copper sulfate, but iron will replace copper and form ferrous sulfate, so whoever exceeds it will form ferrous sulfate.

It is better to use the elimination method for this question, and the wrong option is that it is too absolute.

(1) Answer (a).

A: OH shows negative 1 valence, and two hydroxides are negative 2 valence. Therefore, M in A shows positive 2 valence.

b；Cl shows negative 1 valence, and two chlorates are negative 3 valence. Therefore, M in B shows positive 3 prices.

c；Sulfate shows negative 2 valence, and 3 shows negative 6 valence. And C has two M's, so M shows positive 3 valence.

d；o(2-), so 3 shows minus 6 valence. The same two M, one is positive 3 price.

2): K shows positive 1 valence, so i in ki shows -1 valence.

i2 is elemental, showing 0 price.

H shows +1 price, O shows -2 price, so I in HIO shows +1 price.

You know the rule, -1, 0, +1, and ag shows +1 price, so it shows -1 price. So it's wrong.

3): Answer: (b).

R is +2 valence in oxides, while O is -2 valence, indicating that the chemical formula of the oxide is 60%, then the mass fraction of O is 40%. And the relative atomic mass of O is 16, then the relative molecular mass of this oxide mr(ro) = 16 40% = 40

Is that possible? If you don't understand and ask me again, students should help each other and earn points by the way!!

1 A has only one valence, +2 in A and +3 in the others.

2 The whole permutation is arranged in terms of the valency of i from low to high, then the valence of x is between +1 and +7, so it cannot be agi, because i is -1 valence at this time.

3 R is +2 valence, then the oxide is RO, the mass fraction of R is 60%, then the oxygen is 40%, according to the calculation method of the mass fraction of the elements in the compound. The relative molecular weight is: 16 40%=40 choose b

1.Judging from the title.

The valency of m in a is +2 valence.

The valency of b, c, d is +3 valence.

Because m has only one valence.

So the wrong one is a

2.From the title we see that the valency of i is.

Then the valency of i in x must be between +2---5.

In A, AG is +1 price, so i is -1 price and is not between +2 and +5 price, so it is impossible.

If the positive bivalent is obvious, then the oxide must be worth RO

The mass fraction of r is.

Then the mass fraction of o is 40%.

So the relative molecular weight is 16 B

Design Experiments:

Take a small amount of wall ash and add it to the test tube, and pour dilute hydrochloric acid to pass the gas generated into the clarified lime water Phenomenon and conclusion:

Bubbles bubble up during the test, and the gas produced makes the clarified lime water turbid.

Experimental design: Take a small amount of old wall ash samples in a test tube, and add a small amount of dilute hydrochloric acid to the test tube with a dropper.

Phenomenon: Bubbles are generated during the test.

Operation: Fill the bubbles with the clarified lime water.

Phenomenon: Clarified lime water becomes turbid.

Conclusion: There is carbon dioxide generation, i.e. calcium carbonate in the old wall ash.

Take a small amount of old wall ash in the test tube, pour dilute hydrochloric acid, pour the generated gas into the clarified lime water, and observe the phenomenon.

A large number of bubbles are generated and the clarified lime water becomes turbid.

Design Experiments:

1. Take a small amount of old wall ash and add distilled water to the test tube, and add distilled water, the wall ash is insoluble 2. Add dilute hydrochloric acid to the insoluble substance to produce bubbles, and pass the gas produced into the clarified lime water Phenomenon and conclusion:

Bubbles bubbled out of the test, and the gas produced made the clarified lime water turbid, proving that the old wall plaster contained calcium carbonate.

The mass fraction of carbon in C2H4 is less than 87%, so the mass fraction of carbon in another gas must be greater than 87%.

After calculation, it can be obtained that the conditions in c are satisfied, so c is selected

Metamethylhydrazine is produced after full combustion in O2, and three substances.

Carbon bend size 44=

Elemental composition and carbon fraction of hydrogen-containing metamethylhydrazine.

It is composed of three elements: carbon, hydrogen, and nitrogen.

The mass fraction of carbon without silver.

If the relative molecular mass of metamethylhydrazine is 60, try to find its chemical formula C H N, the ratio of the number of atoms is (:(4:1C2H8N2, and the number is in the lower right corner.