# A factory needs to use dilute sulfuric acid with solute mass fraction of 28% to remove rust for metal. The purchaser bought 2000ml98% concentrated sulfuric acid (density: 1.84g/cm3) from the chemical plant. How many kilograms of 28% dilute sulfuric acid can the worker master dilute it? How many liters of water do you need? My answer is: 2000mL × 1.84g/cm3 × 98％=3.6064kg 3606.4g÷（28％ × 1g/cm3）=12.88L But the correct answer is: 12.88kg 9.2L

## A factory needs to use dilute sulfuric acid with solute mass fraction of 28% to remove rust for metal. The purchaser bought 2000ml98% concentrated sulfuric acid (density: 1.84g/cm3) from the chemical plant. How many kilograms of 28% dilute sulfuric acid can the worker master dilute it? How many liters of water do you need? My answer is: 2000mL × 1.84g/cm3 × 98％=3.6064kg 3606.4g÷（28％ × 1g/cm3）=12.88L But the correct answer is: 12.88kg 9.2L

Your thinking (the mass of solute in concentrated sulfuric acid and dilute sulfuric acid is equal) is right, but you made a mistake in step 2. Step 1: 2000ml × 1.84g/cm3 × 98% = 3.6064kg is the mass of solute. Step 2: 3.6064kg ÷ 28% = 12.88kg is the mass of dilute solution. Step 3: add water to the concentrated solution to become

### Please give some junior high school chemistry questions to answer and explain

1. The following statement is correct ()
A. At present, 109 kinds of elements have been found, and only 109 kinds of elemental elements are composed of these elements
B. A substance that contains only one element must be pure
C. The physical properties of diamond and graphite are different because they are composed of different atoms
D. Both diamond and graphite are simple substances composed of carbon
2. The reasons why CO and CO2 are different in nature are ()
A. CO2 is heavier than air B. CO is insoluble and water C. the molecular structure is different D. the preparation method is different
3. The theme of World No Tobacco Day on May 31, 2006 is "tobacco devours life". Tobacco combustion can produce a toxic gas that can combine with hemoglobin in human blood, which is ()
A.N2 B.O2 C.CO2 D.CO
4. Carbon nanotube is known as the most promising new material in the 21st century. Carbon nanotube is a hollow tube composed of carbon atoms with a diameter of several nanometers (1 nm = 10-9 m)
A. Carbon nanotube is a new type of organic compound
B. If carbon nanotube materials burn completely, the product is carbon dioxide
C. Carbon nanotube material has many pipes, large surface area and strong adsorption capacity
D. The chemical properties of carbon nanotube materials are stable at room temperature
5. The Gulf War caused the burning of a large number of oil wells in Kuwait, resulting in serious air pollution. It is reported that there is black rain in some areas. According to your analysis, the main pollution component forming the black rain is ()
A. Carbon black B. carbon dioxide C. methane D. carbon monoxide
6. One of the reasons for El Ni ñ o is the sharp increase of CO2 in the atmosphere. In order to slow it down, the most ideal fuel is ()
A. High quality coal B. natural gas C. gasoline D. hydrogen
7. The black soled rubber shoes sold in stores have good wear resistance. This is because a wear-resistant filler is added to the rubber, which is ()
A. Graphite powder B. activated carbon C. charcoal powder D. carbon black
8. When preparing carbon dioxide in the laboratory, one of the three instruments is ()
A. Long neck funnel, gas collecting cylinder, water tank B. gas collecting cylinder, conical cylinder, conduit with rubber stopper
C. Alcohol lamp, conical bottle, collecting cylinder D. collecting cylinder, measuring cylinder, long neck funnel
9. Check whether the gas collecting cylinder is full of carbon dioxide. The correct operation method is ()
A. Pour clear lime water into the bottle. B. stretch the burning wooden strip into the bottle
C. Put the burning wooden strip on the bottle mouth D. extend the wooden strip with spark to the bottle mouth
10. The following uses of carbon dioxide are related to both its physical and chemical properties ()
A. Fire extinguishing B. making dry ice C. making chemical raw materials D. making gaseous fertilizer in Greenhouse
11. Calligraphy and painting left over from ancient times, although they are old, still do not change color, because they are used in writing and painting ()
A. Blue ink B. red ink C. blue black ink D. ink
12. The substance contained in the filter tank of gas mask is ()
A. Graphite B. activated carbon C. coke D. quicklime
13. The discovery of semiconductor materials such as silicon (SI) is the basis of the development of computer science and technology. The chemical equation for extracting coarse silicon from quartz sand in industry is 2C + SiO2 = = Si + 2CO. The reaction belongs to ()
A. Combination reaction B. decomposition reaction C. displacement reaction D. oxidation reaction
14. On November 16, 2000, the State Drug Administration urgently warned patients to stop cold medicine containing PPA (chemical formula: c9h14no). The following statement about PPA is correct ()
A. It contains 20 atoms in one molecule
B. The mass ratio of each element is C: H: n: o = 108:14:14:16
C. Its relative molecular weight is 150
D. It is an oxide
15. The similarities in nature between oxygen and carbon dioxide are ()
① Both are oxidizing, ② are reducing, ③ are soluble in water, ④ can react with carbon, ⑤ are gases, ⑥ are oxides, ⑦ can be used for fire extinguishing, and ⑧ is usually more dense than air
A.②④⑤⑧ B.①③④⑤⑥ C.①④⑤⑦⑧ D.①④⑤⑧
1. Choose D
Reason: understanding of the concept of allotrope (several simple substances with different properties composed of the same element)
Homomorphs and heteromorphs are ignored in a, and the number of simple substances can be greater than 109
B, such as diamond and graphite, is a mixture because they are two different substances
They are composed of the same element in C, but the atoms are arranged differently
2. Choose C
Reason: the essence of different properties refers to the difference in chemical structure
3. Choose D
Reason: N2, O2 and CO2 are all components of air. Only CO is a substance that can combine with human hemoglobin, making it difficult to combine with oxygen
4. Choose a
Reason: since it is composed of carbon atoms, nanotubes should be a form of carbon, not organic matter
5. Choose a
Reason: carbon black will combine with rainwater in the air to form black rain, while carbon dioxide is a part of the air. Methane is the main component of natural gas and will not combine with rainwater, nor will carbon monoxide combine with rainwater
6. Choose D
Reason: the first three items are carbon containing compounds. Burning with oxygen will produce carbon dioxide gas, and only burning with hydrogen and oxygen will produce water
7. Choose D
Reason: the physical properties of the other three reflect that their texture is relatively soft. Therefore, they will not wear
8. Choose B
Reason: when preparing in the laboratory, the solid-liquid unheated method can be used to react with marble and hydrochloric acid. Therefore, the alcohol lamp in C can be eliminated. If we do not control the reaction speed, we can not use the long neck loophole, so ad can be eliminated
9. Choose C
Reason: using the non combustion supporting principle of carbon dioxide, how to know the extent of carbon dioxide collection if it is put into the bottle? We don't know whether the wooden strip with Mars extinguishes naturally or carbon dioxide makes it extinguish. Pouring clear lime water can only indicate that there is carbon dioxide gas in the bottle, not how much
10. Choose D
Reason: carbon dioxide is mainly used to extinguish fire, but it is used to sublimate dry ice. It requires a lot of heat and can be used for artificial rainfall. Chemical raw materials mainly use chemical properties. Pay attention to greenhouse gas fertilizer. We know that plant photosynthesis is inseparable from carbon dioxide, which has the function of heat preservation
11. Choose D
Reason: the main component of ink is carbon, which makes use of the stability of carbon at room temperature
12. Choose B
Reason: activated carbon has strong adsorption and can adsorb a large number of other gases
13. Choose C
Reason: the combination reaction is a + B = C, the decomposition reaction is a = B + C, and the oxidation reaction involves oxygen
14. Choose C
Reason: it has 25 atoms in its molecule, and its mass ratio can be reduced. It is an organic substance
15. Choose D
Reason: carbon in carbon dioxide has the highest valence state and can only be reduced, while oxygen usually shows oxidation, so 1 pair. Carbon dioxide can only show oxidation and not reduction. 2 wrong. If they are easily soluble in water, there will be no oxygen in the air, because rain will bring oxygen and carbon dioxide in the air to the water. 3 wrong. Oxygen and carbon can produce carbon dioxide, Carbon monoxide and carbon dioxide can form carbon monoxide with carbon. They are all gases. But oxygen is a simple substance. Oxygen can support combustion and cannot extinguish fire. Their relative molecular weight is 29 times greater than that of air

### A. B, C, D, e, F and G are seven common substances. A is a solid compound containing two elements, C is an oxide indispensable to all life, and F is a blue precipitation. They can react as follows: a + B → C + D; D+E→F↓+G； B+E→C+G Please infer: (1) The chemical formula of C is __ (2) B belongs to______ (fill in "acid", "alkali", "salt" or "oxide") (3) Write the chemical equation of B + e → C + G: __

A is a solid compound containing two elements, C is an oxide (water) from which all life is inseparable, f is a blue precipitation (only copper hydroxide, which is generally mentioned in junior high school), so it can be determined that e is a base, and B + e → water + G, e is a base, so B is an acid. D is the result of AB reaction and can

### In addition to iron powder, a sample may also be mixed with one or two of C powder and CuO powder. Add the powder to a certain amount of dilute sulfuric acid, filter after full reaction, and then add iron powder to the filtrate. Only bubbles are generated on the surface of iron powder, and the filter residue is fully burned in oxygen to produce gas that can make the clarified lime water turbid and solid residue ① The sample must contain C powder and Cuo      ② The sample must contain CuO and may contain C powder ③ The filter residue must contain C powder and Cu       ④ The filtrate must contain FeSO4, H2SO4 and may contain CuSO4 ⑤ The filtrate must not contain CuSO4. The above statement is correct () a. ② ③ ⑤ B. ①④⑤ C. ②③④ D. ①③⑤

Iron can react with sulfuric acid to produce ferrous sulfate and hydrogen, copper oxide can react with sulfuric acid to produce copper sulfate and water, carbon does not react with sulfuric acid, copper sulfate can react with iron to produce ferrous sulfate and copper, the filter residue is fully burned in oxygen to produce gas that can make the clarified lime water turbid, indicating that the powder contains carbon. Add iron powder to the filtrate, and only bubbles are generated on the surface of iron powder, It shows that if there is too much sulfuric acid, all iron will participate in the reaction and the solid residue is copper, so the powder must contain copper oxide. Add iron powder to the filtrate, and only bubbles will be generated on the surface of iron powder, then the filtrate contains sulfuric acid and must not contain copper sulfate. Therefore, D

### Explain the rise of mercury injection when thermometer measures body temperature from the point of view of particles

After heating, it can be considered that energy is obtained. At this time, the potential energy between molecules will increase and the distance between molecules will increase, resulting in the increase of the macro volume of the object, that is, thermal expansion

### What experiment shows that light has volatility? What phenomenon shows that light is particle?

Volatility: 1 double slit interference 2 Poisson Volatility: Poisson bright spot (diffraction),
Particle: 1 is also a device for bimodal interference, but if you change the light into film, you will have bright spots and become bright and dark stripes for a long time
2 photoelectric effect