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Carbon dioxide is generated when the candle is burned, and when the candle is just blown out, part of the carbon dioxide is not in a hurry to completely diffuse, and it is covered by the beaker, and the clear lime water on the inner wall of the beaker will become turbid, thus drawing the wrong conclusion).

Water vapor ) carbon dioxide and water vapor do not burn and do not support combustion ).

White smoke is the carbon dioxide produced when a candle burns, White smoke is the water vapor produced when a candle burns, and white smoke is a small paraffin solid particle formed by the condensation of paraffin vapor.

The purpose of extinguishing the candle and immediately covering the white smoke with a beaker dipped in clarified lime water on the inner wall is to test whether the experiment can reach the correct conclusion in hypothesis 1 (fill in the serial number). The reason for this is that carbon dioxide is also generated when candles are burned.

Extinguish the candle and immediately place a piece of dry and cold glass on top of the white smoke, and find that there is no water mist on the glass piece, indicating that the white smoke is not water vapor.

Extinguishing the candle and immediately reaching for the white smoke with a burning wooden strip (without touching the wax core) found that the candle was re-lit, indicating that the white smoke was flammable and providing evidence for hypothesis 3. Hypothesis 1 can also be ruled out because CO2 does not support combustion

1) Correct Carbon dioxide reacts with clarified lime water to produce white calcium carbonate precipitates.

2) Water vapor.

3) Carbon dioxide will extinguish Mars.

1) No, you can't. Candles burn to produce carbon dioxide.

2) Water vapor.

3) Carbon dioxide and water vapor are non-flammable.

1)①.Yes, carbon dioxide can make clarified lime water turbid.

2) Liquid (3), water vapor is non-flammable.

2CuSO4 + 2H2O = energized = 2Cu (negative electrode) + O2 gas (positive electrode) + H2SO4

A is produced on the pole A, i.e., O2, and A is the positive pole.

At this point, the precipitated solid at the B pole is Cu

After the power supply is reversed, there may be a certain amount of H2O electrolyzed after CuSO4 is completely electrolyzed.

2H2O energized 2H2 gas (negative electrode) + O2 gas (positive electrode) At this time, the amount of O2 generated is, the same; The co-setting of H2 and Cu is generated, and the solution of Cu2+ has a total of Xmol

Then x * 64 + 2 + 32 =x= i.e. the amount of Cuso4 species in the solution is also .

Mass concentration.

Filtration: A method of separating liquids from liquid-insoluble solids by taking advantage of differences in the solubility of substances.

Distillation: An operation method that uses the difference in the volatility of each component in the liquid mixture to partially vaporize the liquid mixture and subsequently condense the vapor part, so as to achieve the separation of the components it contains.

Mixture: elemental or compound.

In chemical change: molecules can be divided but atoms cannot be redivided.

1。Liquids vs. solids.

2。Mutualized fluids with different boiling points.

3。Two kinds of kinds.

4。Molecule atoms.

The ratio of 4a+5b=4c+6d to the mass of the molecule is the ratio of the mass of the molecule. C:D=15:9 for the 4C and 6D generated in the reaction, then the ratio of the mass of C to D: 15*4:9*6 = The mass of D is 3g, so the mass of D is. The law of conservation of mass is obtained.

Mass of B: 3 + = 4g.

Mass ratio: b:c = 4:3

Suppose the relative molecular mass of C is 15 and the relative molecular mass of D is 94A+5B=4C+6D

3g x60/3=54/x x=

b=3g+b:c=4:3

1)fe3

3OH-===Fe(OH)3 (precipitation symbol)2)MgSO4

NH4Cl does not react (because.

The products are all women that are soluble in water, completely ionized, no difficult ionization, precipitation, gas, generated) 3) Ca2++CO32-==

caco3 precipitation symbol).

4) HAC (acetic acid or acetic acid:

ch3cooh

Shi is a weak acid.

I write it without taking it apart.

chemical formula); NH3*H2O (ammonia, weak alkali, do not disassemble, write chemical formula) HAC+NH3*H2O=H2O+NH4++AC-

The elements are all zero-priced. Among the compounds, hydrogen is generally +1 and oxygen is generally -2. Except for the special ones. (hydrogen peroxide, sodium peroxide). In n2h4, n is -2; In n2o4, n is +4;In Hno3, N is +5

So, the highest is Hno3, the lowest is N2H4, and the same is N2, N3, N5, N60

N shows +5 price in HNO3.

N2H4 in N-2 valence.

N2, N3, N5, N60 shows 0 valence (because it is elemental).

N2, N3, N5, and N60 are all pure substances composed of nitrogen elements, which are called elemental substances, and N2H4, N2O4, and Hno3 are pure substances composed of different elements, which are called compounds.

Among them, the highest valency of nitrogen is Hno3, the lowest is N2H4, and the same valency is N2, N3, N5, and N60 are all filled in with chemical formulas).

In n2h4, h is +1 valence, so according to the conservation of valence (i.e., all valencies add up to 0), the valency of n is: +1*4 = 4, 4 2 = 2 valence, that is, n is -2 valence; N2O4 where O is -2 valence, so -2 * 4 = 8, 8 2 = 4, so N is +4 valence; Hno3 where h is +1 valence and o is -2 valence, so -2 * 3 + 1 = 5, so n is +5 valence.

The valency of elemental matter (i.e., pure substance) is 0;

The highest valency of nitrogen is HnO3

The lowest is n2h4

The valency of the same is n2, n3, n5, n60

The highest valency of nitrogen is Hno3, the lowest is N2O4, and the same is N2, N3, N5, N60 (the same is not very certain, based on the elemental valency of 0).

N2, N3, N5, and N6 are all elemental, so the valency is 0, N2H4 is -2 valence, N2O4 is +4 valence, and Hno3 is +5 valence.

Finally, the third-to-last and the first four.