About chemistry 1 junior 3 questions, 1 junior 3 chemistry question.

After the copper sulfate solution and sodium hydroxide solution are mixed, the total mass of the solution becomes smaller, which can also be explained by the law of conservation of mass, because the mass of the solution becomes smaller due to the formation of precipitate, and the total mass of the product is still equal to the total mass of the reactants, but there is a precipitate in the product, and the precipitate should be subtracted when calculating the mass of the final solution, so it is less than the total mass of the reactant.

Because he is talking about the total mass of the solution.

The resulting precipitate cannot be counted in the solution.

SO the conservation of mass has an object.

They're all in one container, and the mass of the container is conserved.

After the copper sulfate and sodium hydroxide solution are mixed, the copper hydroxide precipitate is formed, and the total solute in the solution is reduced, resulting in a decrease in the total solution mass, but the total mass of the substances in the whole system does not change, but exists in the form of precipitation. Conservation of mass refers to the consideration of the whole system level, and when it comes to specific problems, it should be analyzed on a case-by-case basis.

Sodium hydroxide can absorb acidic gases in the air, such as carbon dioxide, so it is not conserved, but it is actually conserved.

The total mass of the copper sulfate solution and the sodium hydroxide solution is equal to the total mass of the sodium sulfate solution and the copper hydroxide produced after the reaction.

Because the reaction of sodium hydroxide and copper sulfate produces copper hydroxide precipitation, the hydroxide and copper ions in the mixed solution are reduced, so the mass of the solution is reduced (the reduced mass is the mass of copper hydroxide. Therefore, the quality is not balanced, so it cannot be explained by the balance of quality.

It's a conservation of mass. However, when the two are mixed, copper hydroxide precipitates are formed. And in the title is the quality of the solution. The precipitate is not counted in the solution.

The reaction equation of sodium hydroxide and copper sulfate is: 2NaOH + CuSO4 = Cu(OH)2 + Na2SO4

The mass before and after the reaction is conserved, because the copper hydroxide precipitate is generated, the precipitate is not in the solution, and the liquid mass of the solution plus the mass of the precipitate can be equal to the sum of the masses of the sodium hydroxide solution and the copper sulfate solution.

zn+2hcl=zncl2+h2↑

So the mass of zinc and hydrogen is the same, because of hydrogen, so zinc 13g, copper 2g

13.(1) After closing the switch, the phenomenon observed in tubes A and B is that bubbles appear on the electrodes, and after a period of time, the volume ratio of gas collected in tubes A and B is about 1:2

The phenomenon in the C tube is the rise of the liquid level.

The reason for this phenomenon is that the hydrogen and oxygen produced by the decomposition of water by electricity increase the pressure in the AB pipe, and the water is pressed into the C pipe.

2) The reason why the gases generated in the A and B pipes are concentrated in the upper part is that the density of hydrogen and oxygen is smaller than that of water, and hydrogen and oxygen are insoluble in water.

14.There are 1234 in physics and 56 in chemistry

15.(1) Both can produce oxygen. (2) The text expression of the third method is to write Chinese without writing the chemical formula. (3) Choose 3, because it is clean, the reaction is also easy to carry out, and it is more economical.

15 1, Heat.

2. Hydrogen peroxide is heated to produce oxygen and water.

3. Choose three, simple, convenient and easy to operate.

14 Physics 1, Chemistry 2, 5, 6

Nature 3, 4

13.(1) The phenomenon of tubes A and B observed by the closing switch is that bubbles are generated on the electrodes, and after a period of time, the volume ratio of gas collected in tubes A and B is about 1:2

The phenomenon in the C tube is the rise of the liquid level.

Reason: Water electrolysis produces oxygen and hydrogen in tubes A and B, respectively, and turns from liquid to gas, and the volume becomes larger, so water is pressed into tube C.

14. Physical Properties: 1,2 Chemical Properties: 5,6 Uses:

3,415·(1) chemical reactions occur to produce oxygen (2) potassium chlorate (arrow) potassium chloride + oxygen; Hydrogen peroxide (arrow) water oxygen (3) choose three, choose one of the reasons: 1, the product is water and oxygen, no pollution to the environment; 2. No need to heat or electrify, save energy, 3, simple and convenient operation.

1: The element is CA

The relative atomic mass is 40

The chemical formula of chloride is CaCl2