The chemical formula of ethanol is C2 h5oh C2 H6 O The "O" above is the English letter

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• 1. The meaning of chemical formula
• 2. The meaning of 2 in c2h6o is () A. There are two carbon atoms in alcohol, B. two carbon atoms C. Alcohol contains two carbon elements D. each alcohol molecule contains two carbon atoms 4. The correct statement about "1,2,3,4" of 4h2co3 is () A. 2 represents two hydrogen atoms in carbonic acid and 3 represents three oxygen elements in H2CO3 molecule C. 4 represents the number of molecules, and D.1 represents that each H2CO3 molecule has a sulfate radical 5. In the following symbols, () A.H B.O2 C.He D.NaCl 6. In water (H2O) and sulfuric acid (H2SO4), it contains () A. The same number of hydrogen molecules B. the same number of hydrogen elements C. the same number of hydrogen atoms D. hydrogen elements 7. The mistake in the following statement is () A. The valence of an atomic group must not be zero. B. some elements have variable valence C. The valence of elements in the simple substance is zero D. nonmetallic elements always show negative valence 8. Among the following substances, those without atomic groups are () A、MgCl2 B、NaNO3 C、Ca(OH)2 D、NH4Cl 9. In chemical terms: (1) Five nitrogen atoms___________ (2) Two hydrogen molecules (3) Three magnesium ions (4) Two hydroxyl ions_______ (5) The most abundant substance in the air (6) Four aluminum ions (7) Hexavalent sulfur________ (8) The smallest particle that maintains the chemical properties of water_____________ . (9) The valence of oxygen in hydrogen peroxide is negative________ (10) Lack of it can lead to thyroid disease 10. The meaning of the value "2" in the following formula is pointed out ⑴2O ⑵O2 ⑶O2- ⑷ H2SO4 ⑸2N2 、 (6)2Mg
• 3. A certain amount of alcohol is completely burned in 96g of oxygen to produce 88g of carbon dioxide and 54G of water Just say the lower quadrant of oxygen
• 4. It is known that alcohol is a mixture of ethanol and water, and the chemical formula of ethanol is C2H5OH
• 5. Does calcium chloride react with hydrofluoric acid? What is the chemical formula Isn't that a strong acid instead of a weak one
• 6. A literal expression for the reaction of seawater in absorbing carbon dioxide________
• 7. Write the following chemical equation: light an alcohol lamp and burn it to produce water and carbon dioxide
• 8. What is the phenomenon of iron wire burning in air, what is the phenomenon of iron wire burning in oxygen
• 9. Literal expression of chemical reaction of burning sulfur, red phosphorus, iron wire and oxygen
• 10. Chemical equation of oxygen production from potassium permanganate
• 11. How much heat do you need to absorb in order to raise the temperature of 4kg water by 50 ℃? If all the energy is obtained by burning alcohol, how much alcohol do you need at least?
• 12. Can 95 degree alcohol spontaneous combustion? What is the spontaneous combustion point?
• 13. How many ml of water is needed to dilute 800 ml of 95% alcohol solution into 76% alcohol solution for disinfection
• 14. Mr. Wang has 60 grams of 90% alcohol. How many grams of water should be added to dilute him to 50% alcohol? To understand some of the stupid level. Thank you!
• 15. 1. How many kilograms of distilled water should be added to dilute 1000 grams of 95% alcohol into 75% medical alcohol? equation
• 16. How many ml of 0.95 medicinal alcohol is needed for 500ml of 0.75 disinfectant alcohol? How to configure?
• 17. 75% alcohol 100ml, how much water is equal to 20% alcohol solution? Please tell us the formula,
• 18. Why is the disinfection effect of 75% alcohol better than other concentrations of alcohol?
• 19. Why can 75% alcohol disinfect? 95%?
• 20. Why use 75% alcohol instead of 95% alcohol for disinfection?