Redox equation balancing, redox equation balancing

The N-element in NH4NO3 is -3 valence in NH4+, and the N-element in NO3-is +5 valence. In the product, n in N2 is 0 valence, and n in Hno3 is +5 valence.

It can be seen that all -3 valence nitrogen is oxidized to N2, +5 valence nitrogen is partially reduced to N2, and the other part is converted to Hno3.

3 to 0 price to 3 price, +5 to 0 price down 5 price, to make the price equal, you need to give -3 price NH4 + with 5, give +5 price NO3 with 3.

In NH4NO3, the two are 1:1, so the whole is matched with 5, and NO3- has two remaining unrestored, and HNO3 is matched with 2, and finally the H2O is balanced according to the H element is 9, and the test is correct according to the oxygen element.

The end result is:

5nh4no3 = 4n2 ↑ 2hno3 +9h2o

There are some problems with the decomposition results of NH4NO3---N2+H2O+HNO3, and the correct decomposition products are as follows:

10nh4no3--8n2+4no2+1o2+20h2o

Nitrogen, one up 3, one down 5, so first in front of N2 with 4Then according to a nitrate group corresponds to an ammonium root and the gain and loss electrons are conserved, so the ammonium nitrate is preceded by 5 and then 2 is matched in front of nitric acid according to the conservation of nitrogen, and the water is accompanied by 5 2, and then expanded twice at the same time.

The trim of the redox equation is as follows:

First, the principle of balancing.

Because there is a transfer of electrons in the redox reaction, the valency of the element must rise and fall, and we call the element whose valency can be increased or the substance containing the element as a reducing agent; Otherwise, it is called an oxidizing agent. From the knowledge of redox reactions, it is not difficult to conclude the balance principle: the total number of electrons lost by the reducing agent = the total number of electrons of the oxidant, that is, the total valence of the reducing agent (element) with increased valence = oxygen.

element) The total valence of the reduced valence.

2. General methods and steps of redox reaction equation balancing.

1. General method: from left to right.

2. Steps: mark the price, find the change, find the total number, and match the coefficient. Namely.

The beginning and end states of the valency of the changing elements are marked;

Beginning State Final State Total Price of Changing Persons = Change CoefficientNote: Suppose that the above changes are expressed in positive valence, where (b-a) (d-c) is.

Lcm.

The coefficient on is filled in in front of the chemical formula of reducing agent and oxidant respectively as coefficient;

Trim other elements by observation;

Check whether the equation after trim conforms to the law of conservation of mass (the ion equation also depends on whether it conforms to the conservation of charge).

Example 1: C + Hno3 (concentrated) - NO2 + CO2 + H2O

Analysis: Bid Variation.

C(0) +hn(+5)O3(concentrated)- N(+4)O2 + C(+4)O2 + H2O

Zhenyu looks for change.

The total number of values that change in the beginning state and the final state = coefficient of change. Find the total.

Matching coefficient. The coefficient of c is 1 and the coefficient of Hno3 is 4, and the other coefficients are leveled by the observation method, and the law of conservation of mass is satisfied after inspection. The chemical equation after trimming is:

C + 4 Hno3 (concentrated) = 4 No2 + CO2 + 2 H2O

3. Special techniques for redox reaction balancing.

1. Right-to-left trimming.

Example 2, Cu + Hno3 (concentrated) - Cu (No3)2 + No2 + H2O

Analysis: Since Hno3 has two roles in the reaction, namely acidity and oxidation, it is more troublesome to match from left to right according to the general method, but if the method of matching from right to left is adopted, this problem is very simple.

Differences: When matching coefficients, only the coefficients in are written before the chemical formula of the corresponding product, and the other steps are the same. The total number of values that change in the beginning state and the final state = coefficient of change.

Cu + 4 Hno3 (concentrated) = Cu (No3)2 + 2 No2 + 2H2O

Summarize the scope of use: This method is most suitable for the type of redox reaction that partially participates in the redox reaction of certain substances (such as nitric acid, concentrated sulfuric acid of royal rental).

The redox reaction equation balancing method is the valence rise and fall method. However, for some complex equations, special balancing methods are required, such as the zero-valent method, the integral method, etc.

1. Trim principle:

The number of atoms of each element before and after the reaction is equal, i.e., the mass is conserved.

The total number of electrons gained by the oxidant is equal to the total number of electrons lost by the reducing agent, i.e., the electrons are conserved.

The total value of the decrease in the valency of the oxidant is equal to the total value of the increase in the valency of the reducing agent.

2. Trim steps:

Standard valence: Write the chemical formula of the reactants and products, and mark the valency of the valence element.

Column Changes: List the rise and fall of the valency of the elements before and after the reaction.

Find the Total: Equalize the total number of increases and decreases in valence.

Matching coefficient: use the method of observation to balance the stoichiometric number of other substances, and after balancing, change the single line to an equal sign.

Check conservation: Check whether the two sides of the equation are "conservation of mass" and "conservation of charge".

3. Some common simple methods are:

Least common multiple method: This method is suitable for common chemical equations that are not very difficult.

Parity Balance: This method is suitable for multiple occurrences of an element on both sides of a chemical equation where the total number of atoms of that element on both sides is odd and even.

Observational balancing: Sometimes there is a substance with a complex chemical formula in the equation, and we can use this complex molecule to deduce the coefficients of other chemical formulas.

Normalization method: Find the key chemical formula in the chemical equation, set the number before the chemical formula as 1, and then balance the number of stoichiometry before the other chemical formula according to the key chemical formula. If the measured number is a fraction, and then the measured number is multiplied by the same integer, and the fraction is turned into an integer, this balancing method in which the key chemical formula measurement number is 1 is predetermined, which is called the normalization method.

Method: Select the most complex chemical formula in the chemical equation, let its coefficient be 1, and then infer it in turn.

The formula and method of the redox reaction equation are as follows:

Trimming of the redox reaction equation.

1. Trim principle: the first is the conservation of electrons, followed by the conservation of charge, and finally the conservation of atoms.

2. Trim steps: standard price change - column change - find the total number - match coefficient - fine inspection. According to the total number of the increase of the valence of the reducing agent and the decrease of the valence of the oxidant, the coefficient in front of the reducing agent and the oxidant is determined, and the coefficient of the oxidation product and the reduction product is determined correspondingly, and the coefficient of other ions (generally the coefficient of hydrogen ion and hydroxide ion) is determined by the conservation of charge on the left and right sides of the equation, and finally the coefficient in front of other substances is determined according to the conservation of atoms.

3. Trim method:

Forward balancing method: if the oxidized and reduced elements are two different reactants, the balancing is usually carried out from the left side of the equation, especially the centering reaction;

Reverse balancing method: For oxidants and reducing agents are the same substance, that is, their own redox reactions or there is only one reactant, especially for disproportionation reactions, it is generally easier to balance the products from the right side of the equation.

For the general redox reaction equation balancing is the basic method: standard valence, column change, find the total, and match coefficient. Then find out the corresponding method according to the type of reaction. Trimming technique formula: Rise and lose oxygen, drop and return, if it is the opposite.

The basic method of the town of the flat base: the valence and elevation method

1. Valence state: write the chemical formulas of reactants and products, and mark the valency of elements with valency changes.

2. Column change: list the change value of the valence of the element before and after the reaction.

3. Find the total number: set the least common multiple of the increase in valency and the decrease in valence as the total number of electronic transfer travel. According to the conservation of electrons, the coefficients of oxidant, reducing agent, oxidation product and reduction product are determined.

4. Matching coefficient: use the observation method to balance the stoichiometric number of other substances, and after balancing, change the single line to the bond land equal sign.

5. Careful inspection: use the three principles of conservation to check whether it is balanced.

The trimming method of the redox reaction equation is as follows: the general method is to match from left to right, mark the beginning and final states before the valence of the changing elements, and use the observation method to balance the other elements, and check whether the balanced equation conforms to the law of conservation of mass. According to whether the reaction has the rise and fall of oxidation number, whether there is electron gain and loss and transfer, whether a chemical reaction belongs to oxidation or bending delay, whether it is a reaction of oxidation or bending.

Redox reaction equation'The balancing method is as follows: the general method is to match from left to right, mark the beginning and final states of the valence of the changing elements, use the observation method to balance other elements, and check whether the equation after balancing conforms to Qiqing's law of conservation of mass. According to whether the reaction has an oxidation number rise and fall, whether there is electron gain and loss and transfer, whether a chemical reaction is a redox reaction, whether it is a redox reaction.

Step 1: List "Oxidizing Agent", "Reducing Agent", "Oxidation Product" and "Reducing Product".

Step 2: Mark the valence state of the variable valence element and the rise and fall of the valence.

Step 3: Trim the number of electrons gained and lost.

Step 4: Trim the number of charges.

Step 5: Check, and write an equal sign.

Reduction-oxidation reaction refers to a chemical reaction in which the oxidation number of an element changes accordingly before and after the reaction. It consists of an oxidation reaction and a reduction reaction and adheres to the law of conservation of charge.

Redox reaction is an important reaction in chemical reactions. Combustion, respiration, photosynthesis in nature, chemical batteries, metal smelting, rocket launches, etc. in production and life are all closely related to this reaction. [