A question about the heat of reaction 10

What experiments that? I just flipped through the book, and I don't have a job

Oh, it turned out to be neutralizing the heat inside, didn't see it

Because the density of hydrochloric acid is greater than that of sodium hydroxide at the same concentration, it is more convenient to calculate the heat energy later, so the NaOH should be excessive.

For example, the density of 1 mol of hydrochloric acid and mol of sodium hydroxide solution can be approximated as 1 gram of milliliter. Therefore, the mass of 50 ml of 1 mol hydrochloric acid m1 = 50 grams, the mass of 50 ml mol molten sodium hydroxide solution m2 = 50 grams, the mass of the solution formed after neutralization is m1 + m2 = 100 grams, its specific heat is c, and the heat capacity of the calorimeter (the instrument for measuring heat, which has the effect of thermal insulation) is c0 (coke).

If the change in the temperature of the solution is T2-T1, the heat released during neutralization is:

Q=[(M1+M2)C+C0](T2-T1) There is another reason: the NaOH solution is easy to absorb CO2 and the NaOH concentration decreases, and the excess alkali can ensure that the acid is completely neutralized, thereby improving the experimental accuracy

In the textbook of the third year of high school, there is an experiment on the determination of the heat of neutralization, in which the amount of hydroxide is slightly more than the amount of hydrogen ions, so that the hydrogen ions react completely? "This is to make the acid-base reaction as soon as possible, and just generate the amount of water that needs the substance, because if the amount of hydrogen ions and hydroxide ions is equal, the reaction is very dilute at the end, the reaction rate is very slow, and the insulation of the system is not 100%, which will cause a large error, so the amount of one substance is greater than the other, that is to say, the amount of hydrogen ions is slightly more than the amount of hydroxide to make the complete reaction of hydroxide.

The heat of reaction refers to the heat released or absorbed by the system when the temperature of the product returns to the starting temperature of the reactant after a chemical reaction occurs under constant pressure and without non-expansion work.

In other words, the heat of reaction usually refers to the heat emitted or absorbed by the system when chemical changes occur in the isothermal and isobaric process. The heat of chemical reaction comes in many forms, such as:

Heat of generation, heat of combustion, heat of neutralization, etc. The heat of chemical reaction is an important thermodynamic data, which is determined experimentally, and the main instrument used is called a "calorimeter".

Heat of Reaction Calculation:

1.Measured experimentally.

According to the specific heat capacity formula, it is calculated: q=cm t, and then the heat of reaction is calculated by q according to the chemical reaction equation.

2.The heat of reaction is directly proportional to the amount of the reactant of each substance.

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

Usually people regard the energy absorbed by disassembling 1mol of a chemical bond as the bond energy of the chemical bond, and the bond energy is usually expressed by 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)

Chemistry book: The heat released or absorbed during a chemical reaction, usually called the heat of reaction. The heat of reaction is denoted by the symbol δh and is measured in kj mol

Encyclopedia: Heat of reaction usually refers to: when a chemical reaction occurs under constant pressure and without non-expansion work, if the temperature of the product returns to the starting temperature of the reactant, the heat released or absorbed by the system is called the heat of reaction.

In other words, the heat of reaction usually refers to the amount of heat emitted or absorbed by the system when physical or chemical changes occur during isothermal and isobaric processes. The heat of chemical reaction comes in many forms, such as:

Heat of generation, heat of combustion, heat of neutralization, etc. The heat of chemical reaction is an important thermodynamic data, which is determined experimentally, and the main instrument used is called a "calorimeter".

Heat of reaction usually refers to the heat of reaction when a chemical reaction occurs without non-expansion work, if the temperature of the product returns to the starting temperature of the reactant, the heat released or absorbed by the system is called the heat of reaction.

There are generally two kinds: isochoric heat of reaction and isobaric heat of reaction. The thermal effect (qv) of the isochoric process reaction is equal to the change in the internal energy of the reaction (δu); The thermal effect (qp) of the reaction in the isobaric process is equal to the enthalpy change (δh) of the reaction

Enthalpy change refers to the increment of enthalpy in which a process takes place in the system.

The isobaric heat of reaction of the system is equal to the enthalpy change.

There are many forms of heat of chemical reaction, such as: heat of formation, heat of combustion, heat of neutralization, etc. The heat of chemical reaction is an important thermodynamic data, which is determined experimentally, and the main instrument used is called a "calorimeter".

Enthalpy changes are the amount of enthalpy changes in the enthalpy of an object. enthalpy is a combination of internal energy and flow work)。

When the chemical reaction occurs under constant pressure and without non-expansion work, if the temperature of the product returns to the starting temperature of the reactant, the heat released or absorbed by the system is called the heat of reaction.

Simply speaking, the heat emitted or absorbed by the system when physical or chemical changes occur in the process of isothermal and isobaric processes.

chemical

reaction

See "Reaction Heat Effects". Referred to as heat of reaction, it is the heat released or absorbed by chemical reactions at isotherm. In principle, the heat of reaction can be determined by two experimental methods:

1) Direct measurement with a calorimeter, for example, the reaction is carried out in a closed vessel, and the heat of reaction can be calculated by energy balance; (2) The reaction equilibrium constant at different temperatures is determined first, and then the thermodynamic formula of correlation reaction heat, reaction equilibrium constant and temperature is used to calculate the heat of reaction. For chemical reactions where it is difficult to control and determine the heat of reaction or equilibrium constant, Gaisce's law proposed by 1840 (the thermal effect of a chemical reaction or physical change is independent of its pathway) can be used. Synthesis from the most stable elementalization at constant temperature using the heat of generation (1

mol of enthalpy of a compound) or heat of combustion (1mol of enthalpy change when a substance is completely combusted) is calculated indirectly.

Because of the different states of reactants and products, the corresponding enthalpy values are different. For example, although liquid water and water vapor are both water, the difference between the enthalpy of the two is the heat of vaporization. The reflected heat is the difference between the enthalpy value of the product in a specific state and the buried enthalpy value of the reactant;

The heat of reaction is the energy difference between the reactant and the product. Stove slag.

If the energy liquid of the reactant is closed, it will be exothermic, and vice versa, it will be endothermic.

The energy of a substance is related to temperature, and a high temperature means high energy, so the heat of reaction is related to temperature.

The energy of the gas is also related to the pressure, so the heat of reaction with the participation of the gas is also related to the pressure. The effect of pressure on solids and liquids is negligible.

However, in fact, it is not greatly affected by temperature and pressure, so it is generally calculated using data at 25 degrees Celsius and standard air pressure.

Different states have different energies, and the three-state transition requires endothermic or exothermic retention, doesn't it? As for the pressure temperature, the change in the state of matter is also affected by these two items.

The second large.

The energy of gases is higher than that of solids, and the same as the products produced means that the first to release more energy. Numerically it is even more negative.

The heat of reaction is a sign comparison, the sulfur element in 1 is that the gaseous energy is higher than the solid sulfur in 2, and the heat released is more, so 1 is less than 2 (because the heat of exothermic reaction is negative, the more heat released, the smaller the heat of reaction).

Please adopt it promptly if you understand!! Good luck with your progress!!

If you look at the state of the reactant product, these two states are different from the sulfur element, and you can take the first sulfur vapor in the middle and cool it down and release it into a sulfur solid, and the reaction is the same as the second one.

But before you cool it to exothermic.

It is equivalent to an extra part of the heat released from the total reaction.

On the other hand, gaseous sulfur has more internal energy than solids, and the reaction products are the same, so it's equivalent to more heat.

s(s)=s(g) δh>0

Reaction: S(S) + O2 (G) = SO2 is the sum of the reaction S(G) + O2 (G) = SO2 (G) and the reaction S(S) = S(G).

So δH2 > δH1

That is, the latter reaction heat is large.

S(g)+O2(g)=SO2(g) reaction heat is larger.

Because sulfur needs to be endothermic from a solid to a gas.

In the second equation, the state of sulfur is solid, and it needs to absorb heat to change to gaseous state and then react, which requires more heat energy.

c2h4(g)+3o2(g)==2co2(g)+2h2o(l)δh=c2h5oh(l)+3o2(g）==2co2(g)+3h2o(l),δh=

2H2(G)+O2(G)==2H2O(L)δH=, turn the second one upside down and add the first one (Geisce's law).

c2h4(g)+h2o(l)==c2h5oh(l),δh=