Chemistry issues. Someone, ask for an answer

1.(1) 500g d (2) Rust of weights; When weighing in a graduated cylinder, look down at the reading;

2.Analysis: Under the condition that the temperature remains unchanged, a saturated solution with an unknown mass fraction is evaporated with part of the water and then returned to the original temperature, and there is crystal precipitation, and the evaporated solution is still a saturated solution

Answer: Solution: a. The mass of the solution is equal to the sum of the mass of the solvent and the solute, and both the solvent and the solute are reduced, so the mass of the solution is also reduced, so a is right;

B. The evaporated solution is still the saturated solution at T, so the mass fraction of the solute remains unchanged, so B is wrong;

c. Once the solute and solvent are determined, temperature becomes the only factor affecting the solubility of solid substances, so C is right

d. After evaporating part of the water, there is crystal precipitation when it returns to the original temperature, indicating that the evaporated solution is still a saturated solution, so D is right;

Therefore, choose B Comment: To answer this question, we should fully understand the relationship between the solute mass fraction and the saturated solution, that is, the saturated solution mass fraction is the largest at the same temperature, and at the same time, it is necessary to pay attention to whether the change process is carried out under the condition of constant temperature.

If you have any questions, you can ask them.

1,,ac,Sodium chloride is more, water is less. 2，b

1ca（oh)2

2 co23 na2co3

4 HCl5 CO2+Ca(OH)2==CaCO3 +H2OCA(OH)2+Na2CO3==CaCO3 +2NaOHca(OH)2+2HCl==CaCl2+H2ONa2CO3+2HCl==2NaCl+H2O+CO2 6 4.

(1) Direct current, small bulb on or not); (2) Add copper sulfate solution drop by drop in the beaker, and the light will be dimmed, filled and brightened, and darkened unchanged); (3) When the two substances happen to react, you can see that the bulb is extinguished (brightened, darkened, extinguished), and then continue to add copper sulfate solution dropwise to brighten, brighten, darken and remain unchanged).

A: sodium hydroxide; B: Sodium carbonate; C: sodium sulfate.

2naoh+co2===na2co3+h2ona2co3+ca（oh)2==caco3↓+2naoh

Ca(OH)2 CO2 Na2CO3 HCLCCA(OH)2+2HCl====CaCl2+2H2ONa2CO3+Ca(OH)2===CaCO3+2NaOH2CO3+2HCl===H2O+CO2+2NaClCO2+Ca(OH)2===CaCO3+H2O2 Bright, Darken, Extinguish, Brighten.

NaOH + CO2 ==== Na2CO3 + H2ONa2CO3 + Ca(OH)2===CaCO3 + 2NaOH (If this question is not related to the previous one, C can be sodium sulfate or something like that.) )

After the reaction, the solids decreased in grams, indicating that grams of CO2 were generated, and C+2CuO==2Cu+CO2

x160：x=44：

x=8g, so the copper oxide in the original mixture is 8 grams, and the carbon is 2 grams.

The mass of carbon cannot be calculated from the mass of CO2 in this reaction because the carbon must be in excess in this reaction.

After the reaction, the solids decreased grams, indicating that grams of CO2 were formed, and in one case C+2CuO==2Cu+CO2

x160：x=44：

x=8g, so the copper oxide in the original mixture is 8 grams, and the carbon is 2 grams.

In the other case, c+2cuo==2cu+co2 y

12：y=44：

y = so copper oxide is gram and carbon is gram in the original mixture.

The synthesis of ammonia from hydrogen and nitrogen is a reversible reaction that cannot be carried out to the end, so the reaction is only the reaction that should be completely reacted, that is, only the reaction of the complete reaction is 1 4.

3h2+n2===2nh3

n0 3mol 1mol 0mol

n 3 4mol 1 4mol 1 2molnt 9 4mol 3 4mol 1 2mol balance, the amount of nitrogen, ammonia, hydrogen has been marked, divided by volume.

The heat of reaction refers to the heat generated by a complete reaction, but it is exothermic at equilibrium, and it does not react completely when it reacts at equilibrium.

If the equilibrium concentration is calculated, I think it can be extrapolated as a percentage of the total heat released from the complete reaction.

I think you're right, the meaning of this question is unclear.

This may be the meaning of his answer.

Because HCO3- is more difficult to ionize than HBRO, the resulting CO2 reacts BRO- to HBRO

So get the answer.

br2+h2o+na2co3==nabr+hbro+nahco3

1.It is easy to make the spilled droplets hurt people.

Look down on the readings. 2.(1) Looking at the color, the purple-red color is copper, and the silver-white color is aluminum.

2) Tested with dilute hydrochloric acid, it is aluminum that can react with dilute hydrochloric acid to produce bubbles, otherwise it is copper.

1.The mouth of the test tube is facing people, and the liquid boiling and splashing will hurt people: take 5ml with a qualified graduated cylinder, but there is actually it, the measurement is not accurate, and the error increases.

2.(1) Aluminum reacts with hydrochloric acid to produce hydrogen.

2) Burn where there is white, there will be aluminum, and copper will turn black.

I can barely read a few words, so I'll answer what I can read clearly!

The one that is most likely to lose electrons is D, which becomes sodium ion Na+ after losing electrons

It is easy to get electrons for b, and the electrons for electrons become fluoride ion f-