How do you calculate the heat of reaction of a substance? H？

h: The heat of reaction of the heat absorbed or released.

The reaction is bad and auspicious.

Calculation formula: qp= u+p v= u+rt in the vb formula u u final state - u initial state u reaction product - u reactant.

where vb(g)= n(g) mol, that is, the difference between the total number of product gas molecules and the total number of reactant gas molecules when a 1mol reaction occurs.

Heat of reaction calculation formula.

Heat of reaction and matter energy relationship: h = total energy of the product - total energy of the reactant; It is also known that the sum of the bond energies of a substance is greater.

stable, the lower the energy it has.

Relationship between heat of reaction and bond energy h = sum of bond energy of the buried object - sum of bond energy of the product.

Reaction heat relation.

1.Measured experimentally.

According to the specific heat. The formula is calculated: q=cm t, and then according to the chemical reaction.

The equation is given by q to find the reaction heat speed.

2.The amount of heat of reaction with the amount of the reactant of each substance.

proportional. 3.The heat of reaction is calculated using bond energy.

Usually people take apart 1mol of a certain chemical bond.

The energy absorbed is regarded as the bond energy of the chemical bond, which is usually expressed in e in kj mol

Method: H = e (reactant) — e (product), i.e., the heat of reaction is equal to the difference between the sum of the bond energies of the reactants and the sum of the bond energies of the products.

For example, the reaction H2(G) +Cl2(G) 2HCl(G);

h=e(h-h) +e(cl-cl) -2e(h-cl)

4.The heat of reaction is calculated from the total energy of the reactants and products.

h = total energy of the product - total energy of the reactant.

5.Calculated based on the heat of combustion.

The heat emitted by the combustion of a substance q=n (combustible) The heat of combustion of the substance.

6.According to Gaisce's Law.

Make the calculations. Gaisce's law: whether a chemical reaction is completed in one step or several steps, the heat of reaction is the same; That is, the heat of reaction of a chemical reaction is only related to the beginning and end states of the reaction, and not to the reaction pathway.

That is, if a reaction can be carried out in several steps, the sum of the heat of reaction of each step of the reaction is the same as when the reaction is completed in one step.

The heat of reaction is the same.

7.It is calculated from the standard molar enthalpy of formation of reactants and products.

For reactions in a certain state"0=σbvb"(This is a way of moving the reactant to the right of the equal sign by shifting the term, in this case, the inverse.)

The coefficient of the reactant is negative) the reaction heat of the reaction is h= bvb fhm, i.e., the heat of reaction is equal to the standard molar enthalpy of formation of all the substances involved in the reaction in that state with the chemical equation of the substance.

The algebraic sum of the products of the stoichiometric coefficients in . This can be demonstrated using Geisce's law and the definition of standard molar enthalpy of formation. Some reference books will have standard molar enthalpy of formation for various substances, which can be consulted to calculate the required heat of reaction.

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According to the heat of combustion data, the heat of reaction is directly calculated by using the formula.

q = heat of combustion n (the amount of combustible substance.

The difference between the total energy of the reactant and the product is calculated, ΔH = E (product) E (reactant).

According to the reactant chemical bond.

Calculation of the energy change during the formation of the chemical bond between the break and the product, δh = the energy absorbed by the chemical bond break of the reactant The energy released by the chemical bond formation of the product.