There are 40 chemistry fill in the blank questions in the third year of junior high school, and ther

1.There are four elements: H, S, O, and Na, please select one of the elements to write a chemical formula with the following requirements: (1) the oxide H2O with the smallest relative molecular weight; 2) acid H2SO4 for rust removal of metal surfaces 3) alkali Na2CO3 contained in kitchen cleaners 4) Na2SO4, a salt composed of three elements;

2.There is a small amount of oxygen dissolved in the water. In the hot summer months, it is often necessary to pour oxygen into the fish pond through an aerator.

The reason is that the solubility of the gas decreases with the increase of temperature, and the amount of dissolved oxygen in the water decreases as the temperature increases in summer, so it is often necessary to pour oxygen into the fish pond through an aerator

The laboratory can use hydrogen peroxide solution to produce oxygen, and the chemical equation of the reaction is 2H2O2= mNO2= 2H2O+ O2 2) Sodium peroxide is also a peroxide, and submarines often use sodium peroxide as an oxygen donant, while maintaining the stability of the air composition in the boat, write the chemical equation of this reaction 2Na2O2+2H2O=4NaOH+O2

4.(1) The valency of chlorine in calcium hypochlorite is 1 2) The chemical equation of calcium hypochlorite reaction with water and carbon dioxide is Ca(clo)2+CO2+H2O=CaCO3 +HClO 3) The preservation method of calcium hypochlorite disinfectant is sealed and preserved

5.(1) The chemical formula of propane is C3H8; 2) There are 11 atoms in a propane molecule; (3) After the complete combustion of propane, water and carbon dioxide are generated, and the chemical equation of complete combustion of propane before the whole combustion is written C3H8 + 5O2= ignition = 3CO2 + 4H2O.

1) H2O water.

2) H2SO4 sulfuric acid.

3) NaOH sodium hydroxide. (On this issue: 85259646 this netizen said that sodium carbonate is wrong, because the title does not have carbon elements).

4) Na2SO4, sodium bisulfate.

There is a small amount of oxygen dissolved in the water. In the hot summer months, it is often necessary to pour oxygen into the fish pond through an aerator. Here's why:

The solubility of oxygen decreases with the increase of temperature, and in summer, due to the influence of high temperature in fish and other animals, the metabolism accelerates, and a large amount of oxygen is needed, and the oxygen is integrated into the water as much as possible through the aeration trace Ashibashi machine. (Students who don't understand this article can imagine boiling water, the temperature is high, there is water vapor coming out, water vapor comes out, and the gas in the water is reduced, so you need to use an aerator (this topic, lhslhp121212 This netizen is wrong to use the principle of hydrogen peroxide, and there is no manganese dioxide as a catalyst).

Hydrogen peroxide solution can be used in the laboratory to produce oxygen, and the chemical equation for the reaction is 2H2O2=H20+O2

Submarines often use sodium peroxide as an oxygen supply, and at the same time maintain the stability of the air composition in the boat, and the chemical equation of this reaction is written NA202+2CO2+H2O=2NAHC3+O2

In this topic, 85259646 and other netizens just used water to react with sodium peroxide, obviously ignoring that in submarines, the role of oxygen supply is because people want to breathe oxygen and discharge carbon dioxide, and sodium peroxide is just in humid air, which can absorb carbon dioxide, which not only releases oxygen, but also absorbs carbon dioxide.

The valency of chlorine in calcium hypochlorite is +1 (positive 1 valence).

The chemical equation for the reaction of calcium hypochlorite with water and carbon dioxide is Ca(ClO)2+CO2+H2O=CaCO3+2HClLo

The preservation method of calcium hypochlorite disinfectant powder is shading, sealing (light action will accelerate the decomposition of hypochlorite, sealing is to prevent moisture and carbon dioxide from reacting with it), so the bottle is not colorless, but a brown bottle.

The chemical formula of propane is C3H8 (both of alkanes are HNCN+2).

There are 11 atoms in a propane molecule (3 carbon atoms, 8 hydrogen atoms, 2 elements have no isomers).

The chemical equation for the complete combustion of propane: C3H8 + 5O2 (Posture Fierce Combustion) = 3CO2 + 4H2O

1 1)h2o 2)h2so4 3)naoh 4)na2so4

2 When the temperature rises, the solubility of the gas in the water decreases, and the oxygen level in the water decreases, resulting in a lack of oxygen in the fish, so oxygen should be introduced for the fish to breathe before the chain.

3 1) 2H2O2 = MNO2 (catalyst) = 2H2O+O2 2)2Na2O2 2CO2===2Na2CO3 O2

4 1) +1 2) Ca(clo)2+CO2+H2O=CaCO3 +HClO 3) Sealed and stored.

5 1) C3H8 2) 11 3) C3H8 + 5O2 = (ignition) 3CO2 + 4H2O

Good luck with your studies!

h2o; h2so4; naoh; na2so4;

The temperature is increased, and the dissolved oxygen is reduced.

2h2o2==2h2o+o2; 2na2o2+2h2o=4naoh+o2;

1; ca(clo)2+co2+h2o=caco3+2hclo;Protect from light, lose the reed wide seal;

c3h8; 11; c3h8 + 5o2== 3co2 + 4h2o

8 cao --ca(oh)2 Answer: Add an excess of H2O

9 HCL --Hno3 Answer: Add an excess of AGNO3

10 H2SO4 --HNO3 Answer: Add excess BA(NO3)2

11 H2SO4 --HCl Answer: Add an excess of BaCl2

12 ca(oh)2 --koh Answer: Add an excess of K2CO3

13 znSO4 --znCl2 Answer: Add an excess of BaCl2

14 ZnCl2---Zn(NO3)2 Answer: Add an excess of AGNo3

15 Cu2(OH)2CO3 --H2O Answer: Heat.

16 H2CO3 --H2O Answer: Heat.

17 Cu(OH)2 --CuCl2 Answer: Add excess HCl

18 hg(no3)2 --cu(no3)2 Answer: Add an excess cu

19 cuSO4 --Na2SO4 Answer: Add an excess of NaOH

20 Na2CO3 --NaCl Answer: Add excess HCl

Some questions have different answers).

Does the landlord mean that the former is transformed into the latter through how it is transformed? ? That's it if so.

10.The addition of Ba(NO3)2, Ba2SO4 is a white precipitate, which can be obtained.

11.Add BACL2, same as question 10.

12.KCo3 is added, and CaCO3 is a white precipitate, which can be obtained.

13.Add BACL2, same as question 10.

14.With the addition of AGNO3, AGCL2 is a white precipitate, which can be obtained.

16.Carbonic acid light can be broken down into H2O and CO2, right? ~？Carbonic acid is unstable.

17.Add MgCl2, Mg(OH)2 is a white precipitate, which can be obtained.

19.Add NaOH, Cu(OH)2 is a blue precipitate, which can be obtained.

20.Add CACL2, same as question 12.

These are what I will, I can't be wrong, I hope it will help the landlord, I am a science, but I have not studied inorganic chemistry for a long time, and some have forgotten. >0<~~

3. The commonly used instrument for taking lumpy solids is a medicine spoon or tweezers, when loading the test tube, the test tube should be placed flat, and the drug is sent horizontally into the test tube, and then the test tube is slowly upright, so that the drug slides slowly; When the test tube is loaded, the test tube is tilted, and the medicine spoon (or paper trough) containing the drug is sent to the bottom of the test tube, and then the test tube is slowly upright to let the drug slide.

4. When taking liquid drugs, the bottle stopper should be inverted on the table, the label should be placed towards the palm, and the bottle mouth should be poured slowly close to the mouth of the test tube. A dropper is commonly used to take a certain amount of liquid, and a pipette is commonly used to take a small amount of liquid.

5. The commonly used instrument for taking solids of a certain quality is the pallet balance; In the process of operation, the object to be measured is placed on the left disk and the weight is placed on the right disk (i.e., the principle of "left object right code"); When weighing dry solid drugs used in chemical experiments, weighing paper must be placed on the left and right trays, and drugs that are prone to deliquescent must be weighed in a beaker.

6. The flame of the alcohol lamp is divided into outer flame, inner flame and flame center, which should be heated at the outer flame part, and the test tube should form a 45-degree angle with the desktop when heating the liquid, first preheated, and then the test tube should be moved back and forth from time to time when heating; When heating the solid, the mouth of the test tube should be slightly inclined downward, preheated first, and then fixed on the iron frame for heating; When clamping the test tube with the test tube clamp, it should be clamped on the upper part of the test tube (or 1 3 places away from the test tube mouth).

3.Tweezers, horizontally, put the mouth of the test tube, slowly stand upright, slowly slide down, medicine spoon, tilt, medicine spoon, paper trough, upright, pour into the bottom of the test tube.

4.Backwards, towards the palm, closely, slowly, covered, graduated cylinder, rubber tip dropper.

5.Pallet balances, items, weights, objects, yards, paper and glassware of the same size.

6.Outer Flame, Inner Flame, Flame Center, Outer Flame, 45 degrees, Preheating, Slightly Lower Tilt, Preheating, Medicine, Upper Middle Part, 1 3