Some doubts about sophomore chemistry, a few questions about sophomore chemistry

I'm also a sophomore in high school.

1. The basic knowledge of molar mass is relatively boring, but it is not very difficult, and there are only a few physical quantities involved.

Mass m, number of particles n, (gas) volume v, molar volume of gas (in standard case, Avogadro's constant na, molar mass m (in fact, this is the relative molecular mass, the only difference is that the molar mass has a unit "g mol"), and the stoichiometric number (that is, the trim coefficient before the chemical equation) is added. There is also the amount of important substance n.

The issue involving density is the relatively high part. This part is the key part of the first year of high school, and it is very theoretical.

The basic formula for correlation is the most basic m=n*m, n=n*na, density=mv, v=n*molar volume of the gas, which can then be derived.

Density * gas molar volume = molar mass m

Because as long as the temperature pressure is constant, the density is proportional to the molar mass.

Maybe that's what you don't quite understand.

Of course, you also need to master a law of Avogadro, and you don't need to memorize the definition, and you don't need to memorize other inverted knowledge. Just remember that at the same temperature and pressure, the volume ratio of the gas = the amount of the substance n ratio.

This part of the knowledge can solve a large part of the problem as long as it firmly grasps the quantity n of matter.

My experience with pressing the bottom of the box is that if you grasp the unit, you can memorize it completely. For example, the problem of density The unit of density is g l (generally speaking) The unit of standard molar gas is l mol, multiply it and look at it, and you get g mol Are you familiar? is the unit of molar mass, so the above formula density * gas molar volume = molar mass m

No rote memorization at all. Simple, isn't it?

2. I feel that this kind of thing is something that is believed in and not believed. Since you dare to say that you are not too bad at chemistry, it means that you are confident enough.

3. In terms of exams, they are nothing more than questions. Once the foundation has been laid, it's okay not to review, and it doesn't take a lot of time.

4. In terms of opinions, let's listen to the ones upstairs.

5. I think I've listed all the relationships in One. Remember, the fundamental quantity grasps the "quantity of matter" and the Avogadro constant.

The above is purely personal opinion.

My chemistry is okay, I studied chemistry in the second year of high school, and I want to learn organic chemistry after the second year of high school, organic chemistry is not easy to learn than inorganic chemistry, but my advice to you is to properly consolidate the classroom knowledge after listening to the class, not too much, just an ordinary information book, don't know how to ask the teacher, to learn to use the knowledge between disciplines to apply,

I think that students who are good at chemistry don't just memorize equations. The key is that the regulations are clear and systematically memorized. Each substance is recorded in the form of a diagram or concept diagram of the properties and main reactions.

The transformation relationship between various substances should be constantly linked. You don't have to do too many questions, but you need to understand the knowledge points tested in each question. And think more, and when you wait until the chemical reaction principle you know the importance of thinking.

I'm about to take the college entrance examination, and I still have confidence in science and chemistry. Happy to you.

1. B silver nitrate - the yellow precipitate is potassium iodide, the light yellow is sodium bromide, the white is sodium chloride, and the turbidity is sodium sulfate;

2. B ether !! Heyhey, it's poisonous

3. b according to the general formula of organic matter combustion:

It is a "gaseous hydrocarbon" and can be set to cxhy

And "full combustion", then the carbon-containing gas generated is only Co by the change of pressure, which can be obtained: 2n(Co)=n(cxhy)+n(O), that is: Cxhy+(x+y 4)o =xco +y 2h o, 2x=1+(x+y 4).

Solution: x=3;y=8.

In the water, there are 2 conditions that will definitely be met.

1. At room temperature, c(h+)*c(oh-)=1e-142, the hydrogen ions and hydroxide ionized by water must be equal. Note that it is made from water in sulfuric acid solution, because the c(h+) ionized by water is very small, it cannot be calculated directly, and h+ can be calculated by calculating oh-

If there is a total of H+, then OH- is 5e-13 (Condition 1) and according to Condition 2, it is concluded that H+ ionized by water is also 5E-13

This value and the production of sulfuric acid are too small to ignore, and it is considered that H+ is all provided by sulfuric acid.

Hope it helps

You can assume that it can react, for example, ferric chloride to produce HCl and Fe(OH)3, and then HCl volatilization. It is explained that it can react, but if it is iron sulfate, H2SO4 and Fe(OH)3 are generated, and the sulfuric acid does not volatile, and the iron hydroxide is immediately neutralized and restored to iron sulfate, so the assumption is not true, that is, it cannot react.

Generally, hydrochloride and nitrate (all hydrolyzed salts) volatilize HCl or HNO3 generated by hydrolysis during heating, and generally do not get the solid of the substance, while sulfate can.