Chemistry questions, in the third year of junior high school, are not difficult!!!!!

When a certain amount of sodium hydroxide solids is added to the small test tube, the liquid level in the U-shaped tube changes as follows: the liquid level on the left side decreases and the liquid level on the right side rises. The reason is that sodium hydroxide dissolves in water and releases heat, which increases the temperature and pressure in the gas collection cylinder.

What if you add ammonium nitrate solids to the small test tube? If ammonium nitrate is added, the liquid level on the left side will rise and the liquid level on the right side will fall.

The water in the U-shaped tube flows to the gas collection cylinder; Because the sodium hydroxide solution will react with CO2 in the air, the air pressure in the gas collector cylinder will be reduced, and the outside atmospheric pressure will press the water into the gas collector cylinder.

As for ammonium nitrate, you just have to look at it 1Can the reaction occur in the gas collector cylinder2Whether the gas is released or "absorbed" after the reaction.

You can also see whether they "react" with water to be exothermic or endothermic, but I think because they "react" in a small test tube first, they have little effect on the gas collector cylinder, but I still quite agree with the above statements.

1) Liquid level rises Sodium hydroxide is dissolved in water and exothermic, resulting in an increase in the temperature of the solution and a rise in the liquid level.

2) Liquid level drop Ammonium nitrate dissolves in water to absorb heat, resulting in a drop in the temperature of the solution and a drop in the liquid level.

The water in the U-shaped tube is pressed outward, because the sodium hydroxide reacts with the water to release heat, and the pressure increases.

Ammonium nitrate, on the contrary, is endothermic.

The drop of the liquid level at one end of the U-shaped tube connected to the gas collection cylinder should be sodium hydroxide, the solid dissolved in water, and the heat release will make the gas expand.

If ammonium nitrate solid is added, the liquid level at the other end of the U-shaped tube should drop because the ammonium nitrate solid is dissolved in water and absorbs heat to reduce the volume of the gas.

The addition of sodium hydroxide is exothermic U-shaped, communicating with the atmosphere in a U-shape, with one side of the liquid level rising and the other side decreasing.

The addition of ammonium nitrate is endothermic and the phenomenon is the opposite of the above.

According to the nature of CO carbon monoxide, it can be known that C2O3 is fully burned only CO2, and the chemical formula 2C2O3 + O2 = 4CO2 can be known that ABC is all right, and then D: 24 72 = 1 3 so for.

The valency of C in C2O3 is +3 valence, and since the chemical properties are similar to Co, it is inferred that A and B are correct, C is obviously correct, and as for D, it can be calculated that it should be, or simply from the chemical formula, it can be directly seen that the mass fraction of O is greater than C, and the D option is wrong.

The answer is D because carbon monoxide is reducible, and A is correct according to the question.

There are only carbon and oxygen elements in carbon trioxide, so c is correct, and the full combustion product is carbon dioxide, so b is correct.

Calculate the mass fraction of carbon: (12*2) (12*2+16*3) = so d is wrong.

Is polyvinyl chloride a polymer material? Yes.

Is polyester a synthetic fiber? Yes, polyester fibers are synthetic fibers, commonly known as polyester.

Can you tell the difference between wool and polyester by combustion? Yes, wool has a smell when burned, and polyester melts without a smell when burned.

Is PVC a composite? No, it is obtained by polymerization of vinyl chloride.

4al + 3o2 ==2al2o3

The ratio of the number of atoms is: 4:3:2

The ratio of relative molecular mass is: 108:96:204, i.e. 9:8:17A:4; 3；2；9；8；17

In the reaction of aluminum and oxygen ignition to form aluminum oxide, from the ratio of the number of atoms and molecules between the reactants, the products, and the number of atoms and molecules, every 4 aluminum atoms react with 3 oxygen molecules to form 2 aluminum oxide molecules, and from the mass ratio between them, every 9 parts of aluminum reacts with 8 parts of oxygen to form 17 parts of aluminum oxide.