Chemical Reactions and Energy Problems Explained .

Solution: It is known that the average reaction rate expressed by the change in the concentration of z is that the concentration of its substance at the end of 2 min is:

Cz = formed at the end of 2min, so the concentration of the substance of W is: Cw = according to the reaction: 2x (g) + y (g) = nz (g) + 2w (g) 2 1 n 2

cx cy so n 2=

2 cx =1 cy=2 The amount of the substance of x involved in the reaction can be obtained, the concentration of the substance of cx = y is the concentration of cy=

2) The average reaction rate expressed by the change in the concentration of x in the first 2 min v(x)=cx t=3) When the reaction is carried out to the end of 1 min, the amount of substances in z nz = the amount of substances involved in x is: 2 nx = 2

So the amount of substance of x in the remaining container is:

1) n=42) The average reaction rate v(x) = mol*l-1*min-1 is expressed as the change in the concentration of x in the first 2 min

3) When the reaction is carried out to the end of 1min, the amount of x substances in the container is filled in the relationship between the quantity or size).

1) At the end of 2min, n(z) = mol n(z) n(w) = 2

n=42) (v(x)/v(z)=1/2)

3) n(x) < because the speed keeps getting smaller.

It can be judged according to the type of reaction, heat change, bond energy, and common reactions, as follows: (1) Exothermic reaction:

The total energy possessed by the reactant The sum of the bond energies of the reactants of the total energy possessed by the product The sum of the bond energies of the product.

Stability: reactant product (the lower the energy, the more stable the principle) h 0, that is, h is " ".

Typical reactions: general combustion, neutralization reaction, reaction between active metal and dilute acid, thermite reaction, conversion from unstable substance to stability, oxidation of metal, most chemical reactions, etc.

2) Endothermic reaction:

The total energy possessed by the reactant The sum of the bond energies of the reactants of the total energy possessed by the product The sum of the bond energies of the product.

Stability: Reactant product.

h 0, i.e. h is " ".

Typical reaction: C (scorching) Co

2. Calcined limestone, water gas, BA (OH).

2·8H2O and NH

4Cl reaction, ionization of weak electrolytes, hydrolysis of salts, conversion from stable to unstable substances, most decomposition reactions, etc.

Hope it helps.

The bond energy of the reactant and the product will be given when doing the problem, for example, the bond energy of the h-h bond is xxkj

The gas mixture can be seen as its heat of combustion.

Whereas the heat of combustion of CH4 is 890

The volume ratio required to release the same heat is V1:V2=Q:Q 890 3:1, and the mass ratio of CO2 generated by combustion is proportional to the amount of C atomic matter, that is, 3*:1*CH4, where the ratio of C is:1=3:2

You just have to list the reactions.

It's definitely clear at a glance.

Energy Change in Chemical Reactions The energy change in a chemical reaction is usually manifested as a change in heat. **When the essence of exothermic and endothermic chemical reactions, we should pay attention to four points: The characteristics of chemical reactions are the formation of new substances, and the total energy of the reactants of new substances is different, because the energy of each substance is different (the essence of chemical reactions is the breaking of old chemical bonds and the formation of new chemical bonds, and the energy absorbed by the breaking of old chemical bonds is different from the energy released by new chemical bonds, resulting in energy changes); The essence of energy conservation in the reaction is that the energy released by the formation of new chemical bonds is greater than the energy of the old chemical bond breakage and is released in the form of other energy. If the total energy possessed by the reactant is higher than the total energy generated, then a part of the energy will be released in the form of heat energy in the reaction, which is an exothermic reaction, and vice versa, an endothermic reaction.

Change in energy in a chemical reaction: The change in the heat of a chemical reaction.

1. Chemical reaction rate - used to measure the speed of chemical reactions.

Expression: Expressed as the change in the amount and concentration of reactants or products per unit of time. In a reaction vessel with constant volume, it is usually expressed as a change in the amount of reactant substances per unit time or a change in the amount of product substances, and the reaction rate is always positive.

It is positive regardless of whether it is expressed as a reactant or a product.

2.Representation: v= dc dt 2Units: mol l or mol ml

Two. Factors influencing the rate of reaction.

Internal Factors – Some factors of the substance itself (size of the particles, properties of the substance, etc.).

External factors: Concentration of reactants; All other things being equal, the greater the concentration of reactants, the greater the reaction rate.

the temperature of the reaction; All other things being equal, the higher the temperature of the reaction, the greater the reaction rate.

Catalyst; All other things being equal, the addition of catalyst can significantly increase the reaction rate.

The smaller the particles of the solid reactants, the larger the contact area of the reactants, and the greater the reaction rate.

Change in energy in a chemical reaction.

1 Endothermic reaction and exothermic reaction.

The breaking of an old chemical bond requires the absorption of energy, and the formation of a chemical bond requires the release of energy (the essence of a chemical reaction).

If it is an endothermic reaction, the total energy of the reactants is less than the total energy of the products, and the energy is absorbed during the reaction.

In the case of an exothermic reaction, the total energy of the reactants is greater than the total energy of the products, and the energy is released during the reaction.

1.Denote;

The rate of chemical reaction can be expressed in terms of or per unit of time.

2.Representation: v= 2Unit: or.

3.Peculiarity. All positive values are taken and are the average rate.

The same reaction is represented by different substances, and the values are not necessarily the same.

For the same reaction, the ratio of the rate expressed by each substance is equal to the ratio of the stoichiometric number (equal to the ratio of the amount of change of each substance).

4.Factors influencing the rate of reaction.

Internal Factors -- Determinants).

External factors: Concentration of reactants; All other conditions are the same, the concentration of reactants and the greater the reaction rate.

the temperature of the reaction; All other things being equal, the temperature of the reaction and the rate of the reaction are greater.

Catalyst; All other things being equal, the addition of a catalyst can significantly reduce the reaction rate.

The particles of the solid reactants, the contact area of the reactants, and the larger the reaction rate.

1) Exothermic, endothermic reactions are related to the bond energy of the substance, but it cannot be linked to the mass. This is a chemical change, which is a reaction between atoms and does not involve the inside of the atoms. The mass change occurs during a nuclear reaction, so the two are unrelated.

2) Why do some chemical reactions emit heat, while others need to absorb heat? It is rotten due to the fact that the energy possessed by various substances is different. If the total energy of the reactant is higher than the total energy of the product, then when a chemical reaction occurs, a part of the energy will be converted into heat energy and other forms of release, which is an exothermic reaction.

If the total energy possessed by the reactant is lower than the total energy possessed by the product, then in the event of a starvation chemical reaction, the anti-clearing reactant needs to absorb energy to be converted into the product, which is the endothermic reaction. It can be seen that the process of chemical reaction can also be regarded as the process of converting the energy "stored" in the substance into heat energy and being released, or the heat energy being converted into the energy inside the substance and being "stored".

Here's a diagram of the activation energy for you.

E1 can be seen as the energy to be absorbed by the breaking of old chemical bonds.

E2 can be seen as the energy released by the formation of new chemical bonds.

e is the total energy of the reactants.

E end is the total energy of the product.

So the heat of reaction is equal to the total energy of the reactant and the total energy of the product. This diagram is an exothermic reaction, can you understand this?

It is not possible to add or imagine, and it is also possible to multiply the equation by a constant and then add or subtract. Without looking for an intermediate, you *2+ * get 2C(S)+2H2(G)+O2(G)=CH3CoOH(L), H=(

If the reactant of the given equation is the reactant of the equation, then the equation needs to be equal, and the coefficients need to be equal before adding, if the reactant of the equation is the product of the empty ballast formula of the equation, then the equation is added, and the coefficients need to be equal before subtracting.

The equation can be obtained by excavating the square collapse excavation range 2 2 + 3 2-1 known to the beam type, and the same reaction heat can also be found as the aggregate slag nucleus.

With the increasing tension of oil resources, the development and utilization of natural gas resources have received more and more attention. Using natural gas as raw material to balance chemicals through syngas (CO, H2) is the leading technical route for natural gas conversion and utilization, and the main processes are as follows: (1) partial oxidation of methane.

ch4(g) +1/2o2 (g) =co (g) +2h2(g) ，h = kj/mol。This reaction is a spontaneous reaction under certain conditions. Some studies believe that the mechanism of partial oxidation of methane is:

CH4(g) +2O2 (G) =CO2(G) +2H2O(G) ,H1 =— KJ mol CH4(G) +CO2 (G) =2CO (G) +2H2(G) ,H2 = KJ mol CH4(G) +H2O (G) =CO (G) +3H2(G) ,H3 of H3 reaction H3 = 2) Methane water vapor catalyzed reforming. As shown in the figure, hot helium gas flows in from below to provide energy during the reaction.

The mixture composed of methane and water vapor flows from the upper part of the catalytic tube, and the endothermic reaction occurs, and the mixture comes out from the lower end and then enters the central tube upwards. Gas Inlet Temperature Inlet Pressure MPA Inlet Flow Outlet Flow Methane Methane CO2 Catalytic Rereforming. At high temperatures, the reason for this significant decrease in reaction rate may be a decrease in catalyst activity.

4) Partial oxidation of methane coupled with reforming. Natural gas-fueled off-gas (mainly CO2, H2O, O2 and N2) and methane can be used directly to produce syngas. Alphabetical number) a Direct use of CO2 in flue gas can reduce CO2 emissions on a large scale b The outlet temperature of flue gas is high, which can significantly save energy c The use of appropriate catalysts can increase the conversion rate of methane.

Students, the liquid state needs to absorb heat when it becomes a gaseous state, that is, the energy of SO2 (L) is greater than that of SO2 (G), H = raw trapped ant - reactant, so compared with the raw ruler bridge into SO2 (G), the disadvantage of burying SO2 (L) is to put less energy, hope!

The transformation of the gas rock into a liquid state requires the release of energy.

That is, the gaseous energy is higher than that of the jujube brother, and the energy released by the substance with high generation energy is relatively small, and it may be chaotic or to generate a liquid state.

SO2 is more energy emitted.