 # 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)

## 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