Solve two chemistry questions in junior high school, and ask for detailed solutions to chemistry pro

Iron is dissolved in sulfuric acid to release hydrogen, 10g of iron powder is added to 50g of dilute sulfuric acid in the total mass of 60g, but the quality of the filtrate after filtration is , it means the mass of hydrogen and impurities generated, and the hydrogen is generated xg and impurities yg. The system of equations obtained by the chemical equation (x 2)*56+y=10

x+y=。To get the solution, then use the mass of hydrogen to find the iron mass, and then calculate the mass fraction.

Copper oxide is dissolved in dilute sulfuric acid to produce copper sulfate and water, and no gas is discharged. Copper and zinc alloy are dissolved in dilute sulfuric acid, copper does not react, and zinc reacts with dilute sulfuric acid to form zinc sulfate and hydrogen. That is, the hydrogen actually released in the right plate (the balance is balanced left and right, and the right and left side are 8) can calculate the mass of zinc (.

I've explained it in such detail, it's a bit too much to say if I don't give one!

1. +fe=>56%

The complete reaction of 50g of sulfuric acid is regarded as a limiting reagent of iron, and the mass ratio of iron to hydrogen is 56:2, so + g is equivalent to g of iron to generate g of hydrogen away, so iron is g, that is, 56%.

2.Dilute sulfuric acid does not react with copper, and copper oxide produces copper sulfate and water, and the quality remains unchanged. The gram on the right is less, which means that the gram of hydrogen is reduced, and the mass ratio of zinc to hydrogen is 65:2, so gram zinc participates in the reaction.

If this kind of thing is filled in the blanks, it will be pushed directly, and it will be pushed directly through the mass fraction and reaction coefficient (oral calculation), and if it is a short-answer question, then it will be an equation. Then it's just a verbal calculation, which is generally made up, and if it is not made up, then it is calculated in writing.

As far as the first question is concerned, according to the conservation of mass, we know that the mass before and after the reaction should be equal, but the mass of the filtrate obtained after the reaction is 10+50=60g before the reaction, so we know that the difference between them is the total mass of the hydrogen generated and the impurities filtered out. Therefore, we can assume that the mass of iron is x, the mass of impurities is y, and the mass of hydrogen produced is x|, according to the chemical reaction equation28, so we can get the system of equations x+y=10,x|28+y=, solve x is the mass of iron, and divide the mass of iron by 10 to get its mass fraction.

Question 1: From 18GH2O, we can see that there must be 2GH2 16GO2 in it, and then you add 2G to H2, which is 4:16=1:4,A; Add to o2, that is, 2:18=1:9, no.

2gh2 16go2 2gn2

So choose C for the second question

H2 + O2 = Ignition = H2O

x y 18g

4/x=32/y=36/18

x=2g y=16g

Because there is 2 g left, if it is H2, the ratio is: 16:4=4:1, if it is oxygen: 18:2=9:1

There is no 9:1 option in the question.

So choose A2 and get it from the above question: generate 18g of water.

There must be 16g of oxygen and 2g of hydrogen.

The two add up to 18g

There is also 2g of nitrogen

So it is impossible to have hydrogen and oxygen left.

But the option doesn't why?

Question 2: Select C. There is no need to calculate at all. Since the reaction produces water, hydrogen and oxygen must not coexist.

Question 1: Generate 18 g of water.

There must be 16g of oxygen and 2g of hydrogen.

The two add up to 18g

There are also 2g that can be nitrogen, hydrogen and nitrogen, oxygen and nitrogen.

Question 1; The main thing is to write out the chemical formula for each option! Then observe whether FE reacts with dilute sulfuric acid to produce more or less gas! I didn't count!

Lazy · · If you have more, you should choose the one that generates more gas. If there is less, choose the option that generates less gas. Actually, you really can't write... Sometimes, for a single multiple-choice question, it is enough to calculate whether the gas generated for each option is more or less!

Because the only one who is right is the only one! But it's better to figure it out!

Question 2; Magnesium and magnesium and magnesium copper and aluminum alloys of the same mass produce the same gas, so the mass of Cu, and Zn to produce the same gas as their total mass of mg can be proportional! Count it well!

1: Large, inverted CO2 experiment.

2：3，na2o2+co2 ->na2co3 + o2

Consumes CO2 and is easy to obtain; No need to consume other energy, save energy; And it's convenient, simple, and secure.

The secret of the big "dog death hole": there is a hill in Italy and there is a cave in the mountain. It is common to see small animals such as puppies and kittens running into this hole and never coming out.

Someone lit a candle and went into the cave to look for it, only to find that the critters were dead in the hole. When he placed the candle on the ground and was about to carefully examine the cause of the critter's death, the candle went out. In order to find the cause of the death of the small animal, someone took the puppy into the hole again.

As a result, as soon as the puppy entered the hole, it had difficulty breathing, struggled desperately, and died in less than a few minutes. But the man is safe in the cave. Therefore, people called this hole "dog death hole".

Why do dogs die when they get into their holes, but people are unharmed?

People enter the cave to observe, find that there are stalactites and stalagmites in the cave, it is certain that this is a limestone cave, limestone (the main component is calcium carbonate) meets groundwater, will decompose carbon dioxide, the bubbles that emerge from the rock cracks of the cave are carbon dioxide gas, carbon dioxide is heavier than air, gathered at the bottom of the cave, dogs are shorter than people, they are surrounded by carbon dioxide, of course they will suffocate to death after a long time, people will bend down and bow their heads will also feel difficult to breathe, and the candle will extinguish itself, all of which illustrate this problem.

1. Carbon dioxide can be collected by the upward air method.

2、③2co2 + 2na2o2 ＝2na2co3 + o2

It makes full use of the carbon dioxide gas exhaled by people, and does not need to be heated or electrified, and the reaction conditions are simple and the operation is simple.

CO2 is denser than O2 In a closed glass enclosure Two candles of different heights can be placed After a period of time, it can be observed that the lower candle goes out first, and the upper layer goes out later.

1. Big in the deep well does not get air into the feeling of panic.

2. The third best principle is to write the equation,,, the advantages are: the carbon dioxide exhaled by people can be used as raw materials,,, solid is easy to carry and safe. And the amount is large.

Big. 3 advantages: no heating, convenient and safe.

The first one is that the carbon dioxide is 44 and the air is 29

For example, carbon dioxide is collected by the upward air exhaust method.

The second and third best is that you don't need to do it at room temperature.

Large, collect carbon dioxide using the upward emptying method, there are two candles in a bottle with upper and lower candles, pour carbon dioxide into them, and the lower ones are extinguished first.

2, the third is the best, the principle Na2O2+CO2 ->Na2CO3+O2 advantages, fast, convenient and safe.