How to use the least common multiple of junior high school chemistry?

It's used when writing chemical formulas... That is, you just look at the valency of each element, and then find the least common multiple of these numbers, and multiply the valence by the algebraic sum of the number to 0...

For example, phosphorus and oxygen. When phosphorus shows positive pentavalent, oxygen shows positive bivalent, and the least common multiple of +5 and +2 is 10, then there are 2 phosphorus and 5 oxygen. It's P2O5...

When there are two elements in a compound, the absolute valence value of each other is taken as the number of its own elements, and then simplified (some compounds cannot be simplified). For example, phosphorus is pentavalent oxygen is bivalent, that is, the +5 of phosphorus is regarded as the number of oxygen.

Actually, this thing... There's a lot of chemistry. It's useless... If you see a lot of those chemical formulas, you will naturally write...

As for the common multiple... This is elementary school math yes...

For example, the common multiple of 6 and 8 is to multiply 6 and 8 into the form of prime factor multiplication, 6 = 2 * 3, 8 = 2 * 2 * 2, and then see that 6 and 8 have a set of common divisor 2, so use "common divisor * common divisor number of groups * remaining numbers" is 2 * 1 * 3 * 2 * 2 = 24

If there is a lot of common divisor, it is also multiplied like this, for example, 72 = 3 * 3 * 3 * 2 * 2 * 2 * 2 * 7 * 5, and it is 3 * 2 * 2 * 2 * 2 * 5 * 7 = 1680

Just cross it. For example.

h o writes the valency (absolute value) of o in hydrogen.

Just write the h on the oxygen and simplify it.

..What does this have to do with chemistry?

Formula method

1. If two numbers are coprime, then their least common multiple is the product of these two numbers.

2. If there is a multiple relationship between two numbers, then the larger number is the least common multiple of these two numbers.

3. If the two numbers are not coprime and there is no multiples relationship, the larger number can be expanded by 2 times and 3 times in turn、......When you see which number you expand to first, it becomes a multiple of the smaller number first, and that number is the least common multiple of the two numbers.

Short division

This is the most typical and basic method, and it is also a method that students often use when solving practical problems, which is characterized by being fast and not easy to make mistakes.

For example, find the least common multiple of 24 and 32, [24,32] = 2 2 2 3 4 = 96, where is the common factor of 24 and 32, and 3 and 4 are their unique factors. Of course, finding the least common multiple of three numbers can also be solved by short division, but in the process of division, the quotient must be reached until the quotient is two pairs of mutual elements.

Decomposition factor method

The so-called factorization method is to decompose the factors of two numbers separately, find the common factors and the unique factors, and then multiply them. For example, find the least common multiple of 24 and 32:

This approach requires a clear understanding of the meaning of common factors and common multiples.

Simplification of fractions, cross-contrast method

Simplifying fractions, intersecting and multiplying, can also quickly find the least common multiple of several numbers, for example, find the least common multiple of 2 4 and 3 6:

First, write the numbers 24 and 36 as true fractions or false fractions, and turn them into the simplest fractions, and then cross-multiply them by 24 3=36 2=72, and 72 is the least common multiple of 24 and 36. This method is simple and only requires two steps, one is to simplify the fraction, and the other is to cross-multiply. After discovering this method in teaching practice, Mr. Fang and Mr. Liu from the Teaching and Research Office of Shangrao County, Jiangxi Province once wrote an article summarizing it.

The common multiple of two or more integers is called their common multiple, and the smallest common multiple other than 0 is called the least common multiple of these integers. The least common multiple of the integers a,b is denoted as [a,b], and similarly, the least common multiple of a,b,c is denoted as [a,b,c], and the least common multiple of multiple integers is also denoted by the same notation.

The concept corresponding to the least common multiple is the greatest common divisor, and the greatest common divisor of a, b is denoted as (a, b). Regarding the least common multiple and the greatest common divisor, we have this theorem: (a,b)x[a,b]=ab(a,b are integers).

The method of factoring prime factors can easily find the least common multiple of two numbers. For example, find the least common multiple of 60 and 42.

60 = 2 2 3 5, 42 = 2 3 7, least common multiple of 60 and 42 = 2 3 2 5 7 = 420. In this method, 60 and 42 are separated by prime factors, and only one of the same prime factors (such as 2 and 3) is observed and all the unique prime factors are multiplied into them, and the product obtained is the least common multiple of these two numbers.

Since the results of the two numbers are equal to the product of the greatest common divisor and the least common multiple of the number in a row. i.e. (a,b)*[a,b]=a*b, where (a,b) denotes the greatest common divisor of a and b, and [a,b] denotes the least common multiple of a and b. To find the least common multiple of several natural numbers, you can first find the least common multiple of two of the numbers, and then find the least common multiple of this least common multiple and the least common multiple of the third number, and then continue until the last one.

The resulting pure least common multiple is the least common multiple of the numbers sought.

Step 1: Find the least common factor of two numbers, divide the column short, and remove these two numbers with the least common factor to get two quotients.

Step 2: Then find the least common factor of the two quotients, and remove the two quotients with the least common factor to get the two quotients of the new level.

Step 3: And so on until the two quotients are coprime numbers (i.e., the two quotients have only a common factor of 1).

Step 4: Multiply all the common factors and the last two quotients, and the product is the least common multiple of the two numbers we require.

The least common multiple is the least common multiple of two numbers, for example, the least common multiple of [2,4] is 4,[3,6]=3,[4,8]=8

You can match the false equation, for example: c (insufficient amount) + o2 ignition co However, it is obviously easy to see that this is wrong, the least common multiple is an integer, so it is written as 2c+o2 (insufficient amount) igniting 2co. Another point, for example, if you make 4c+2o2 (insufficient amount) to ignite 4co

This is also your mistake, because both sides can be removed at the same time, so let me tell you, there are fractional integers, there are multiples greater than 1, so that the coefficient is divided by this multiple, I hope to adopt... Not easy.

You find a question, and I'll analyze it for you.

The least common multiple method is a common method for balancing junior high school chemical equations, but it cannot be used to balance all junior high school Zhengyun chemical reaction equations, such as:

co+fe2o3---fe+co2；To balance the above chemical reaction equation method: see that the number of atoms of O in "Fe2O3" is 3, just match 3 in front of "CO" and "CO2", and then match 2 in front of "Fe", and get: 3CO+FE2O3=High temperature code rent=2FE+3CO2

Basically, it's okay, but it's not okay in high school, and high school has to use valence leveling, and it's best to learn

For example, iron oxide and carbon monoxide react.

The topic gives you two numbers, if these two socks can be divided, then continue to divide until there is no common divisor other than 1, then multiply the two numbers that are contracted and then multiply by all the common divisors of your contract, that is the least common multiple, such as 8 and 60, the two have a common divisor divided by 2, and the two numbers become 4 and 30, and the common divisor 2, He Chong then divides by 2 at the same time, and the two numbers become 2 and 15, at this time there is no common divisor except 1, then multiply 2 and 15, and 2 times before, multiply by 4 (2 times 2), so the least common multiple of 8 and 60 is 120.

If there is no common divisor other than 1 for the two people who are given, then it is good to multiply the two directly, such as 5 and 7, and the least common multiple of these two numbers is 35