How to write a chemistry test is the easiest, and I can t remember it clearly I m a junior high sch

Writing a chemical equation starts with identifying the type of reaction it belongs to (not necessarily the four basic reaction types) so that you can quickly judge the product empirically. For example, as long as the cations and cations are exchanged in the metathesis reaction, the redox reaction only needs to be based on the judgment of the substances that are generally produced after oxidation or reduction, which requires more practice to have the wealth of experience.

After the reactants and products are clear, they need to be balanced, for simple reactions, they are directly balanced by the observation method, and the observation method has some skills, such as taking the matter apart (often disassembling water into OH and H), such as treating the reaction as a two-step process (such as calcium hydroxide and carbon dioxide reaction, as CO2 reacts with water to form carbonic acid and then with calcium hydroxide to form calcium carbonate and water, and water is eliminated on both sides, and this equation completes the balancing), and the redox reaction uses the conservation method of gain and loss electrons (not required in junior high school). If it is really not matched, you can also use the undetermined coefficient method, for example: NH3+CL2 - NH4CL+N2 Let the stoichiometric numbers of each substance be A, B, C, D.

System of Column Equations a=c+2d (satisfies the equality of the number of nitrogen atoms) 3a=4c (satisfies the equality of the number of hydrogen atoms) 2b=c (satisfies the equality of the number of chlorine atoms) Let b=1, solve: a=8 3, c=2, d=1 3 8nh3+3cl2=6nh4cl+n2 As long as there are four numbers satisfying all the listed equations, they can be used as coefficients for a set of equations. The common feature of the coefficients of these groups is a:

b：c：……The values of are equal.

Our goal is to find the simplest set of integers to use as coefficients for the equation, so let one of the numbers be a definite value, find the value of the other three numbers at this time, and then use the least common multiple to find the simplest set of integers. Of course, sometimes it is possible to encounter multiple sets of solutions with different proportions that satisfy the listed equations, and theoretically they can all be used as equation coefficients, but the actual coefficients can only be determined through experiments.

Finally, my personal opinion is that these methods are best used to derive chemical equations that you have not learned, and the chemical equations in books still need to be memorized well, after all, you can only talk about skills with a foundation, after all, junior high school is the time to lay a foundation, if you start to trick it, it is very detrimental to your learning, and it is also very time-consuming. Once this level is over, getting started is quick.

This is not simple, the shortcut is at all, read the book well, and you are not afraid of anything after you understand it. I have to write more, but I can't just look at it.

Know the commonly used valence, and then cross and turn into the simplest ratio, understand that the metal element symbol is in the front, the oxygen element symbol is in the back, find the commonality, and the acid root must be in the back.

Commonly used element symbols and structural graphics and simple chemical reaction formulas and formula balancing.

Chemical terms, names and symbols of common elements and atomic groups, non-metals: o oxygen h hydrogen n nitrogen cl chlorine c carbon p phosphorus s sulfur, metal, k potassium ca calcium na sodium mg magnesium al aluminum zn zn zinc fe iron cu copper hg mercury ag silver mn manganese ba barium, atomic clusters (roots): hydroxide, nitrate, carbonate, sulfate, phosphate, ammonium.

The main thing is to read the textbook, for junior high school and high school chemistry, the textbook is king, the chemical equations, the properties of the elements, when you are very familiar with the textbook, and even know which knowledge point is on which page, your chemistry will be almost learned.

3.You can read the textbooks for the common chemical formulas in junior high school, and find the most frequent chemical formulas in them, which are precipitation in general chemical equations.

4.If there is no precipitated gas in the reactants, this is because it is difficult to observe the changes of substances in general chemical reactions, but if there is precipitated gas, it can be easily observed and has particularity.

5.Common elemental valence formulas, monovalent hydrochloride, potassium, sodium, silver, divalent oxygen, calcium, barium, magnesium, zinc, tripentanitrogen, phosphorus, trivalent aluminum, copper, mercury, 12, iron, tri, 2, 4, hexasulfur, 4 valence, many elements have valence, different conditions and different valences.

6.Common atomic clusters (roots) chemical valence formulas, monovalent hydroxide nitrate, divalent carbonate sulfate, trivalent common phosphate, usually negative valence ammonium removal, proficient in dictation of common elements of commonly used valence.

Listen well in class and memorize it well. Junior high school chemistry is very simple