Junior High School Chemistry Competition 100 points award .

Choosing C: Fe3O4 and Fe2O3 for one Fe with 4 3 and 2 3 O's respectively, assuming that it is completely converted to Fe3O4, then about is generated; Assuming that Fe2O3 is completely generated, 8G is obtained; The same is true for FEO.

What we get in the question is that the mixture must have a higher substance, so C is chosen

Using the median value method: assuming that all of them are converted into one substance, only Fe2O3 will be exceeded, so only C can be selected

The initial mass of sulfuric acid is:

Let the zinc involved in the reaction have xmol and xmolh2 is generated at the same time, the increased weight mass = the mass of zinc participating in the reaction - the mass of hydrogen generated, i.e. x= so the mass of sulfuric acid that is reacted is the remaining sulfuric acid.

The total mass of the solution at this time is , so the mass fraction of sulfuric acid at this time is.

The net mass gain is the addition of Zn minus the hydrogen released.

Corresponding to the change in the chemical equation 63 = 65-2

Then the equilibrium mass of ZnSO4 is .

The mass of the solution is the mass of the original solution+

Ignite the first question: HCl is H2+Cl2*****2HCl

a It is not possible for hydrogen and oxygen to exist at the same time after ignition.

I don't think B c should be chosen because HCl is highly soluble in water, and HCl in both should be present in the resulting solution. So if I give the answer only d

Question 2: Personal thinking is not necessarily right.

Question 2: Fe+H2SO4====FeSO4+H2 mass increase ZN+H2SO4====ZNSO4+H2 mass increase.

Acid whole m x m y

Reactions 98 98

x= y=The metal added at this time should be greater than or equal to.

Then the difference in quality between the original two beakers is.

There is a surplus of acid. Fe+H2SO4====FeSO4+H2 mass gain ZN+H2SO4====ZNSO4+H2 mass gain.

m x2 m y2

If the acid happens to be fully reacted, the metal iron and zinc are required, and the added iron and zinc are equal, so when the acid is left, the mass m of iron and zinc should be less than or equal to the substitution of the following formula.

56/m=54/x2 65/m=63/y2

x2=27m/28 y2=63m/65

Poor quality for. Question 3: I also calculate 2:7

Question 4: SO3 + H2O ====H2SO4

5kg*20%=1kg x=

Question 5: Use the relational method.

The mass of oxygen in x

The mass of the oxygen element in y

In R2O, there is 2R---O In R2O5, there is 2R---5O

2r 16 2r 80

r＝12 r=

In R2O3, there are 2R---3 O In R2O5, there are 2R---5O

2r 48 2r 80

r= r=In r2o, there is 2r---o in r2o7, there is 2r---7o

2r 16 2r 112

r＝12 r=

In R2O, there are 2R---O In R2O3, there are 2R---3O

2r 16 2r 48

r＝12 r=

This is my understanding of this problem, you look at the value of this question, if there is no mistake, is the data wrong.

At least, according to this idea, it is necessary to find a group with the relative atomic mass of r equal.

The first t sensation is problematic - -Cl2, HCl can be soluble in water.

H2 reacts with O2 to form water which is liquid, and the remaining H2 reacts with Cl2 to form HCl. So yes.

H2 can be burned in Cl2;

My gut tells me it's the unit that's wrong;

You're right; He's right;

Not really.

For the first time, the crystals have been precipitated, so after precipitation, the solution reaches a saturated concentration.

The second precipitation process is the analysis process of the saturated solution.

Two eutectolic grams.

A total of evaporation is only spring and water.

So after two precipitations, there are still grams of saturated solution left.

From the second step of precipitation, it can be seen that in the saturated solution, the gram crystals are dissolved in water.

So the rest of the gram saturated solution, the substance content is gram.

The content of the substance in the original solution is grams.

The mass fraction of the solute in the original solution is.