![](data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" viewBox="0 0 72 71" width="72"></svg>)
Science, related chemistry (grade 2) The answer to the description of NaNO2, Na2O2, SO2, O2 and other four substances: they all contain two oxygen atoms Why is it wrong? (2 is in the lower right corner)
Some chemical formulas can represent not only the composition of this substance, but also the molecular composition of this substance. This chemical formula is also called molecular formula. For example, oxygen chemical formula O2 is also the molecular formula of oxygen, indicating that there are two oxygen atoms in an oxygen molecule. H2O is both the chemical formula of water and the molecular formula of water, indicating that there are two hydrogen atoms and one oxygen atom in a water molecule, P2O5 is the chemical formula of phosphorus pentoxide, which means that there are two phosphorus atoms in a phosphorus pentoxide molecule
So you should say that each molecule contains two oxygen atoms!
Do you understand?Yes or No?
When it comes to scientific chemistry, it's urgent A lead-acid battery uses 28% dilute sulfuric acid. If one liter of concentrated sulfuric acid with a solute mass fraction of 98% (density of 1.84 g / cm3 _ L) is used, the mass of dilute sulfuric acid is __ kg
If one liter of 98% concentrated sulfuric acid with solute mass fraction (density: 1.84 g / cm3) is used, the mass of 28% dilute sulfuric acid = 1000 * 1.84 * 98% / 28% = 6440g = 6.44kg
It is known that the density of oxygen is 1.429g/l and the density of nitrogen is 1.251g/l. Try to calculate the mass ratio of oxygen to nitrogen in the air (the content of oxygen in the air is 21% and the content of nitrogen is 78%)
M oxygen: m nitrogen = 21 * 1.429:78 * 1.251 = 30.009:97.578
1. In the 2A + B = = 3C + D reaction, it is known that 25 g a reacts exactly with 10 g b to produce 5 g C. when 6 G D is produced in the reaction, how many grams of a participate in the reaction? 2. In the reaction of mixed heating of potassium chlorate and manganese dioxide to produce oxygen, if the mass fraction of manganese dioxide in the mixture is increased from 25% to 30%, what is the decomposition rate of potassium chlorate?
1. According to the mass conservation, the reactant is 25g a + 10g B, and the product is 5g C + D. therefore, if the reactant is 35g and the product is 5g C, then d must be 30g. When 6Gd is generated, only 1 / 5 is lost, so the A, B and C involved in the reaction should be 1 / 5. Therefore, the C 1g generated by a 5g and B 2G involved in the reaction
1. A mixed gas may contain SO3, SO2, and O2, so the following mass fraction of sulfur in the mixed gas is impossible () A 30% B 40% C 25% D 50% 2. A package of mixture composed of Na2S, Na2SO3 and Na2SO4. After analysis, it is found that the mass of oxygen-containing element is 22%, so the mass fraction of sulfur in the mixture is____ PS: all numbers in the title are subscripts The most important thing is to process thank
1. Extreme hypothesis method: it is assumed that the mass fraction of sulfur element in O2 gas is 0, so the answer can only be a small number. If the question is single choice, the answer is d. (if it is not single choice, just calculate the mass fraction of sulfur element in SO2 gas, and the mass fraction of sulfur element in mixed gas is between "mass fraction of sulfur element in SO2 gas" and 0“
2: The molecular ratio of the three substances Na: s is 2:1
If the mass of oxygen is 22%, Na2S accounts for 78% (1-22%)
If Na2S accounts for 78%, the mass fraction of sulfur is very good
Element M has only one valence. If the relative molecular weight of chloride of M is known to be a and the relative molecular weight of nitrate of M is known to be B, the valence of element M is , The relative atomic mass of M is .
If you set the valence of element M as X and the molecular weight as K, then the relative molecular weight of chloride of M is a = K + 35.5x, equation 1, and B = K + 62x, equation 2. You can form equation 1 and equation 2 into a system of first-order equations of the second academy of Sciences, and you can get the answer that the valence of element M is (B-A) / 26.5 and the relative molecular weight of M is a-71 (B-A) / 53.5
RELATED INFORMATIONS
- 1. If 5.6 g of iron powder is completely oxidized to Fe2O3 powder, the mass of oxygen consumed is _____, Its chemical equation is_________
- 2. (senior one chemistry) how many moles is 5.4 ml of water at 4 ° C
- 3. How to find the number of atoms in a substance
- 4. What is the mass ratio of 2molo3 to 3molo2? What is the ratio of the number of molecules? What is the ratio of the number of oxygen atoms? At the same temperature and pressure, what is the ratio of the number of CO and CO2 molecules in the same volume? What is the ratio of the number of atoms? What is the mass ratio?
- 5. High one chemical difference method
- 6. The density of the mixed gas composed of carbon dioxide, hydrogen and carbon monoxide is the same as that of nitrogen at the same temperature and pressure. Then the volume ratio of carbon dioxide, hydrogen and carbon monoxide in the mixed gas is () A. 29：8：13 B. 22：1：14 C. 13：8：29 D. 26：16：57
- 7. Add 50ml 2mol / L H2SO4 solution to the mixture of Fe3O4 and Fe in a certain amount, and just dissolve the mixture completely under certain conditions, releasing 448ml (under standard conditions) gas. Add KSCN solution to the resulting solution, and there is no red. Then fully react with the mixture of the same mass with sufficient CO at high temperature, and what is the mass of iron?
- 8. A small beaker containing hydrochloric acid of the same volume and concentration of the same substance is placed in each of the two plates of the tray balance. After adjusting the balance, add Fe powder and Zn powder of the same quality to the two beakers respectively. The following phenomena are impossible () A. At the beginning, the zinc adding end of the balance rises B. Finally, the zinc added end of the balance rises C. The final balance is still balanced D. At last, the iron adding end of the balance rises
- 9. After a certain amount of zinc is fully reacted with 100ml18mol / L concentrated sulfuric acid, the zinc is completely dissolved and the gas a33.6l (standard condition) is generated. Dilute the reaction solution to 1L and measure that C (H +) = 0.1mol (1) Composition of gas a（ (2) What is the volume ratio of the components in a（ (3) The mass of zinc consumed in the reaction is（ (4) The total amount of material that transfers electrons in the reaction is () moles? I'm counting 1.H2 SO2 2.H2:SO2=13:2 3.95.5g 4.3.4 moles
- 10. What is the value of a in the fine structure formula of alkali metal atomic spectrum So what is its calculation formula?
- 11. Oxygen gain must be oxidized and oxygen loss must be reduced, right
- 12. Add the solutions of the following four substances a into four beakers containing 10ml 2mol / L hydrochloric acid respectively, and dilute them to 50ml with water. At this time, a and hydrochloric acid react slowly, and the maximum chemical reaction rate in the middle of the period is () A.10mL 1mol/L B.20mL 1mol/L C.10mL 2mol/L D.20mL 2mol/L
- 13. Explore whether chemical reaction can occur between potassium carbonate solution, dilute hydrochloric acid and barium hydroxide solution Pour all waste liquid into the same clean beaker. What is the final solute in the indicator beaker? I think potassium chloride and barium chloride are possible, but some people say potassium chloride must be. Why?
- 14. Ammonia and hydrochloric acid are mixed in equal volume. How to write proton conservation? How did you analyze it Equal concentration
- 15. Is the formation of water and oxygen by hydrogen peroxide an oxidation reaction? By the way, if the reaction produces oxygen, but there is no oxygen in the reactant (as reflected by hydrogen peroxide), is it an oxidation reaction?
- 16. Normal saline is a sodium chloride solution with a mass fraction of 0.9% When treating patients with severe dehydration acidosis, the mixture of normal saline and sodium bicarbonate solution is commonly used. The mixture can be prepared with 2.0kg normal saline and 1.0kg sodium bicarbonate solution with a mass fraction of 1.4%. The mass fractions of chlorine and sodium in the mixture are basically the same as those in plasma Please calculate the concentration in 100.0ml plasma: Mass of chlorine= Mass of sodium= (write the calculation formula, and the plasma density is regarded as 1.0g / cm ^ 3) Please write down the reason Can you say it more carefully? Some parts still don't understand
- 17. How to prove that diamond is a simple substance composed of carbon
- 18. How to measure the degree of high voltage electric energy? Active watt hour meter: 349.7, reactive watt hour meter: 311.0, rated dynamic stability current ratio: 185 times, rated short-circuit thermal current ratio: 75 times, and the progress of connecting transformer is 40 / 5 amps Q: can the power consumption of the user be calculated according to the above data? Yes, what is the power consumption?
- 19. For a batch of cement, 12 tons are used, and the rest is 5 tons 9. How many tons of this batch of cement?
- 20. Why control the content of sulfur trioxide in cement