Chemistry questions, help, I ve asked them all over again, and I can get extra points if I answer th

1.In the process of water vaporization, the water molecules do not change or "do not change"), but the molecular spacing is changing, so it is a physical change, and the chemical properties of water before and after the change do not change (fill in "change" or "change"); In the experiment of electrolysis of water, oxygen is obtained at the positive electrode and hydrogen is obtained from the negative electrode, and the volume ratio of positive and negative gases is 1:2

2.It is very dangerous to use hard water in the boiler, because the calcium and magnesium content in the hard water is high, which is easy to produce pot scale, so that the boiler boiling water is heated unevenlyThe way to reduce the hardness of water in life is to use alum to settle and filter

3.There are 6 kinds of substances: ice, carbon dioxide, air, liquid oxygen, iron, and hydrogen, of which the mixture is air, the compound is ice, carbon dioxide, and liquid oxygen, and the oxygen molecule is liquid oxygen

Invariant state of matter.

Physics. No change.

Oxygen. Hydrogen.

The ratio of the number of oxygen atoms to hydrogen atoms in a water molecule is 1:2

The calcium and magnesium ions in the hard water will precipitate to the boiler wall and cause the boiler to heat unevenly, which will cause ** (this space should have a concise answer in your books, which is roughly what it means).

CO2 gas is passed and then precipitated and filtered.

Air, ice, carbon dioxide.

Air, liquid oxygen.

1.Constant, state, physical force change, constant, oxygen, hydrogen, 1:2, water is composed of two elements: hydrogen and oxygen.

2。Hard water heating produces calcium carbonate and magnesium hydroxide precipitation, clogging pipes and causing boiler to occur. Boil.

3。Air. Ice, carbon dioxide,

Air, liquid oxygen.

1 unchanged molecular spacing physical unchanged hydrogen oxygen 2:1 The ratio of hydrogen to oxygen atoms is 2:1

2 After heating, the dissolved ions in the water will be deposited in the boiler due to the reduced solubility, resulting in uneven heat conduction. Bring to a boil before use.

3 Air, Ice, Carbon Dioxide and Liquid Oxygen.

One reagent can be used--- barium chloride, bacl2, it can be and sulfuric acid.

Potassium reaction not only generates barium sulfate to precipitate sulfate ions, but also generates potassium chloride, which does not need to be removed.

Two reagents can also be used--- a reagent added first has a precipitation generation, this reagent must be in addition to sulfate, generally add barium hydroxide first, generate barium sulfate, remove sulfate ions, so that there are more hydroxide ions in it, so a reagent added later is to remove hydroxide, so add HCL hydrochloride to remove OH-, so that all the impurities are gone.

Barium chloride is added first, then potassium carbonate (to remove excess barium ions), then hydrochloric acid (to remove excess carbonate), and then heated to remove HCl

Do an experiment like this: Add dropwise directly.

Potassium carbonate. solution until it happens to be airless. Use 3 ml of potassium carbonate solution to v. Zheng Que found that v3 was greater than v2, which explained.

Sodium hydroxide. Sulfuric acid can be neutralized, otherwise v3 should be equal to v2.

b Potassium carbonate indicates that the acid has been completely neutralized by the base.

Children, study hard, as long as you are willing to use your brain, any knowledge is easy to learn well.

According to the equation of iron mass equality before and after smelting, it is as follows:

560*（100%-4%）=x*（100%-20%）*2fe/2fe+3o

x=960t

Hematite is Fe2O3, according to the conservation of iron element, 560t of pig iron containing 4% impurities, there are tons of iron, Fe2O3 tons are needed, and because of the impurities, 936 tons of hematite can be found according to the percentage.

First use 560*(1-4%) to calculate the mass of the required iron atom, and then calculate the mass of the required pure hematite according to the mass fraction of iron in hematite (56*2) (56*2+16*3), which should be 768, and then divide the resulting answer by 20%.