Help with chemistry? Thank you! Two chemistry questions, thank you!

1. When electrolysis, remember that the cathode is connected to the negative electrode of the power supply, which must provide electrons, so the reaction that occurs at the cathode is the reaction of obtaining electrons, and the electrons that can be obtained are either inactive metal cations, or H+ (in acidic solution), or water (in neutral or alkaline solution). Then look at what electrons can be obtained in the solution: Mn2+, H+, H2O, the world is more active than H, and it is in an acidic solution, so it is H+ that gets electrons.

The reaction is: 2h+ +2e ==h2. Shock return key.

Mn2 + mnO2 needs to lose 2 electrons, so the theoretical yield of mnO2 through 2mol of electrons in the circuit is 1mol.

Attached: The anode reaction is: Mn2+ +2H2O - 2E ==MnO2 + 4H+)

2. The so-called ionic anti-ming should refer to the substances participating in the reaction or the substances whose products exist in an ionic state. A and B are molecules participating in the reaction, and the products are carbonic acid (H2CO3) and ammonia (NH3·H2O), respectively, so they are not ionic reactions. In CD, like nitric acid and mercury nitrate, they exist in an ionic state in water, so they are ionic reactions.

1,2Cu+O2==2Cuo C+O2==CO2 By the law of conservation of mass, copper to copper oxide increases the mass of oxygen that reacts with it, and carbon becomes carbon dioxide, all disappearing into the air, because the solid mass remains unchanged after full combustion in the air, we can know that the mass of carbon is exactly equal to the mass of oxygen reacting with copper. Therefore, the mass ratio of copper powder and toner powder in the original mixture = 2 * 64:32 = 4:1

2，fe+2hcl=fecl2+h2

56 2xx = grams, which is calculated when assuming that all grams of iron are pure iron, in fact it is less than grams, then there are two possibilities for impurities, one is not to react with hydrochloric acid, and the other is that the relative molecular mass is greater than 56

According to the title, only zinc is greater than 56, and it is 65. Pick D.

Cu, C---cuo The mass of oxygen replaces the mass of carbon, will you forget it?

Grams of iron will produce grams of hydrogen, and now there is less, and the hydrogen production ratio should be mixed with greater than: of. Zinc, of course.

Step 1:

2Na2S+3SO2==2Na2SO3+3S Yellow precipitate appears at this time

Step 2: Na2CO3+SO2=Na2SO3+CO2Na2SO3+S= =Na2S2O3

At this point, the solution is clear and becomes a near-neutral solution.

Step 3: Sulfur dioxide is reintroduced to cause Na2S2O3 to precipitate Na2S2O3·5H2O crystals due to the dissolution equilibrium shift.

The total reaction formula: 2Na2S + Na2CO3 + 4SO2 + 15H2O = 3Na2S2O3·5H2O + CO2

The first precipitate is S elemental and the second precipitate is Na2S2O3

From the fact that the solution is exactly neutral, we know that c(h+) = c(oh-), so 2 = c(h+) = c(oh-) = multiplied by 2 because only half of the filtrate is taken.

For every 1 mol of H2SO4, 2 mol of hydrogen ions are ionized, so the amount of hydrogen ions is equal to twice the amount of sulfuric acid of the substance, n(H+) = 2N(H2SO4).

n(h2so4) = / 2 =

The amount of sulfuric acid, the concentration of sulfuric acid is, find the volume.

v(h2so4) = n(h2so4) / c(h2so4) = = = 50ml

The amount of barium chloride is known The amount of hydrochloric acid is calculated according to the chemical equation of the reaction between barium chloride and sulfuric acid, and the total amount of sodium hydroxide is known.

The total number of sodium hydroxide is subtracted from the amount of sodium hydroxide that reacts with half of the hydrochloric acid to get the amount of sodium hydroxide that reacts with sulfuric acid, and then this quantity is used to calculate the sulfuric acid reacted, and then multiplied by 2 to get the number of moles of sulfuric acid that is easy to be in the original sulfuric acid The original sulfuric acid concentration is known, so that the volume of the original sulfuric acid can be calculated.

From left to right, from top to bottom: mol relative molecular mass n m v mol l n v