What are the methods of chemical calculation problems How to do chemical calculation problems

The key is to master the equations and know what products can be generated, so that the calculations can be handy.

To do chemistry calculations, we first need to understand the question type.

High school chemistry calculations are mainly divided into two categories: one is the macro calculation of basic concepts such as the amount of substances, solubility of substances, solution concentration, pH, heat of combustion, etc.; The other is the comprehensive application of various problems with computational factors in the knowledge content of common elements and their important compounds, the basics of organic chemistry, and chemical experiments. In previous years, this kind of test question also appeared in the college entrance examination, so students must pay attention to it.

1. The connection between various basic concepts and calculations.

High school chemistry calculation is the weakness of many students, and it is also easy to lose points, so this part of the knowledge must be understood thoroughly, the following are common methods of chemical calculation, learn it with me I hope it can help everyone!

2. Common methods of chemical calculation.

Conservation method: The regular column calculation is based on the law that some physical quantities do not change at the beginning and end state before and after the change in the reaction system.

Difference method: According to the equation of the chemical reaction of the substance, find out the difference (standard deviation) between the reactant and the product from the beginning state to the final state and the difference between the actual chemical reaction (actual difference).

Calculating the average method: This is a method commonly used in handling mixtures. When two or more substances are mixed, in whatever proportion, there is always an average of some aspect, the mean of which must be between the relevant maximum and minimum values.

As long as you grasp this feature, you can make the calculation process.

Simplified Relational Method: For the multi-step reaction system, the quantitative relationship between the starting substance and the final solution substance can be found, and the proportional formula can be directly listed for calculation, which can avoid the cumbersome intermediate calculation process with fierce belts.

The essentials of solving chemical calculation problems are as follows:

1. The chemical equation should be balanced.

2. The pure quantity needs to be substituted with the equation.

3. The unit of quantity can be used directly, and the upper and lower units should be the same.

4. When encountering two known quantities, we should find the shortcomings to carry out.

5. When encountering a multi-step reaction, the silver should be instructed to use the relational method.

6. Regarding the calculation of the solution, the solution is one or several substances dispersed into another substance to form a uniform.

1. In the calculation of stable mixtures, the quality of solutes, solvents and simple solutions should be accurately analyzed.

Let's set the unknowns to. Then write the chemical equation for this, e.g. c + o2 = CO2

Indicate unknown and known numbers, e.g. 12, 32, 44

Suppose you know that there are 24g of sulphur, how much sulphur dioxide can you produce with enough oxygen? 24g x

List the proportional formula 12 44---24g x solution to get x=88 final answer.

In my own experience, I just need to understand the variables and constants and their interrelationships.

Electronic quantity balance, price balance 、、、

From the problem, it can be seen that the problem is calculated in a saturated solution, in the saturated solution, the mass fraction of the solute solubility (solubility 100g), and then the value in the problem is substituted into the above equation to calculate.

Solution: Because the solution at 25 is a saturated solution, then.

Let the methyl substance be x at 25

x 100g + x) 100% = 30% x = 100g x 30% 1 - 30%) The answer is:

I don't think you need to memorize chemical equations, but you need to solve chemical equations 200 percent. Especially when doing multiple-choice questions like you said, most of the chemical formulas are in your head when solving the problem, and a few values need to be written down on the draft, and you should be able to give the answer without too much calculation. According to the college entrance examination standards, the basic multiple-choice question is 90 seconds per question.

Therefore, it is important to be proficient in the use of chemical equations, both in and out of textbooks.

Without memorizing equations but being able to remember them without confusion, my experience is to memorize the chemical properties of an element according to the periodic table (by major group, by period), and then generalize to the properties of the main compounds of that element. According to the law of periodic change of elements, it is actually very easy to remember, and there is a chapter in the textbook of the third year of high school (Shanghai) dedicated to the gradual change of chemical properties on the periodic table.

If you're not in your third year of high school yet, I highly recommend you take this chapter first!

According to this method, you will soon be able to understand why there are those products according to the chemical properties of the reactants, and it will be easy to remember, and even compare the same and different substances produced by the reaction of reactants of similar chemical properties, which in turn will deepen your understanding of the chemical properties of these substances. To a large extent, I think this is a kind of macro understanding. After mastering this method, my experience has taught me that even if you are given an unfamiliar chemical formula, you can quickly deduce the product with only the reactants.

And this is precisely an important way to solve the data questions in the college entrance examination.

It is important to first understand the relationship between the principle and the knowledge. Only when you have a clear idea can you write down the question.

Master the general steps of each question type and follow them later.

The key is to lay out the equation and list the relationship between the quantity and concentration of the substances used in the bar, and then it will be clear at a glance