Sodium nitrite ammonium salt dissolves and absorbs heat

The dissolution of salts is the process of dispersing anions and cations bound together by ionic bonds (which can be approximated as electrostatic attraction) into water, and then water molecules enclose them separately to form hydrated ions. It's like pulling apart a positively charged ball and a negatively charged ball that were originally very close together, and it takes energy to overcome the attraction. That is, to absorb heat.

The formation of hydrated ions is the process by which ions attract water molecules closer to each other, thus releasing a certain amount of heat, and the closer the water molecules are pulled closer to the ions, the more heat is released. However, the ammonium ions are relatively large and the water molecules cannot be pulled very close, so relatively little heat is released. For most salts, the process of "forming hydrated ions" does not emit as much heat as the anions and cations absorb when they disperse.

As a result, most of the dissolution of salts is endothermic, and ammonium salts are typical of them.

This is my content about substances dissolved in water and exothermic being selected as the essence, please refer to it.

There are two processes in which a substance is dissolved in water, one is that water breaks the chemical bonds of the original substance (for example, sodium carbonate is dissolved in water, and the ionic bonds between the original sodium carbonate are broken by water), which requires energy absorption. Another process is the combination of the formed ions with water to form hydrated ions, and this process releases energy.

The final thermal effect of a substance dissolved in water is the combined result of these two processes, if the energy absorbed by the previous process is less than the energy released by the formation of hydrated ions, then the dissolution process is an exothermic process, such as sodium carbonate, Naoh, sulfuric acid, etc. On the contrary, it is an endothermic process, such as the dissolution of ammonium nitrate is an endothermic process. When the energy of the two processes is about the same, it is basically neither endothermic nor exothermic, such as the dissolution of NaCl.

There is an ionic bond between nitrate and ammonium in ammonium nitrate. When dissolved, energy is required to break the bond energy of this ionic bond, so it absorbs ambient heat when dissolving. Causes the temperature to drop.

It is mainly ammonium salts that absorb heat, and the chemical reaction that absorbs heat is called endothermic reaction. The total energy of the reactants in an endothermic reaction is lower than the total energy of the products. The stronger the energy (bond energy) of the chemical bond in the product, the stronger the qualitative position of the stable file; The weaker the energy, the worse the stability.

From a chemical point of view, I think it will be very simple and very vernacular, as follows:

Ammonium nitrate dissolves and absorbs heat because it takes energy to break the chain of ammonium ions and nitrate ions, which will absorb heat in water, so its solution will cool down.

Sodium hydroxide dissolves and exothermic, and the reason for this is the opposite.

If you dig deeper, it will be beyond the scope of chemistry, and it will be difficult to understand if it belongs to the category of chemical physics.

When a crystal dissolves, it needs to absorb a large amount of heat because ionization destroys its lattice energy.

Ammonium nitrate (NH4NO3) is an ammonium salt, which is a colorless and odorless transparent crystal or a white crystal, which is highly soluble in water, easy to absorb moisture and agglomerate, and absorbs a lot of heat when dissolved. Decomposed by violent impact or heat, decomposed by alkali.

Some countries have formulated regulations on the production, storage and transportation of ammonium nitrate for agricultural purposes, and some countries even prohibit the transportation and direct use of ammonium nitrate as fertilizer, and only allow the use of calcium ammonium nitrate made by mixing it with calcium carbonate.

Storage precautions: Store in a cool, ventilated warehouse. Keep away from fire and heat sources.

It should be stored separately from combustibles, reducing agents, acids, and active metal powders, and should not be mixed. The storage area should be equipped with suitable materials to contain the spill. Vibration, impact and friction are prohibited.

During the dissolution of ammonium nitrate, the molecules or ions of the solute diffuse into the water, and this process is endothermic.

Extend and extend

When a substance is dissolved, two processes occur at the same time: one is the solute particle, the molecule or ion leaves the solid (liquid) surface and diffuses into the solvent, this process absorbs heat, which is a physical process; Another process is the particulates of solutes – molecules or ions and solvent molecules that generate solvates and release heat, which is a chemical process. These two processes are not equal to the heat absorbed and released for different solutes, when there is more heat absorption than heat release, for example, when potassium nitrate is dissolved in water, because it is unstable in combination with water molecules, it absorbs more heat than it emits heat, it is manifested as endothermy, and when it is dissolved, the temperature of the solution decreases.

Conversely, when there is more exothermic than endothermy, for example, when concentrated sulfuric acid is dissolved in water, because it and water molecules form mutually stable compounds, and more heat is released than it absorbs, it is manifested as exothermic, so the temperature of the solution increases significantly.

Most ammonium salts, nitrate dissolved in water are not endothermic processes.

Exothermic: sodium hydroxide, potassium hydroxide, quicklime (liquid: concentrated sulphuric acid).

Endothermic: ammonium and nitrate.

Basically unchanged: NACL

When a substance is dissolved, why is there endothermic or exothermic phenomenon?

This is because: the dissolution of matter, on the one hand, is the particle of solute - molecules or ions have to overcome their own attraction to each other to leave the solute; On the other hand, the dissolved solute needs to diffuse into the entire solvent, and these processes require energy, so when the substance is dissolved, it must absorb heat. This is the reason for the temperature drop during the dissolution process.

If the dissolution process is just simple diffusion, it should all be endothermic, so why is there exothermy? It turns out that in the process of dissolution, the solute particles, molecules or ions, not only separate from each other and disperse into the solvent, but also the solute particles dissolved in the solvent can also form solvates (hydrates if the solvent is water) with the solvent molecules, and heat is released in this process.

Thus, when a substance is dissolved, two processes take place at the same time:

One is the solute particles - molecules or ions leave the solid (liquid) surface and diffuse into the solvent, this process absorbs heat, which is a physical process;

Another process is the particulates of solutes – molecules or ions and solvent molecules that generate solvates and release heat, which is a chemical process.

These two processes are not equal to the heat absorbed and emitted for different solutes, when there is more endothermic than exothermic, for example, when potassium nitrate is dissolved in water, because it is unstable in combination with water molecules, it absorbs more heat than it emits, it is manifested as endothermy. When dissolved, the temperature of the solution decreases, on the contrary, when the exothermic is more than the endothermic, for example, when the concentrated sulfuric acid and sodium hydroxide solids are dissolved in water, because it and the water molecules form mutually stable compounds, the heat released is more than the heat absorbed, it is manifested as exothermic agitation, so the temperature of the solution increases significantly.

Whether the temperature of a substance dissolved in water increases or decreases depends on the amount of heat absorbed or released by the two processes during the dissolution process. If:

Q suck q put.

The temperature of the solution decreases;

Q suck q put.

increased temperature of the solution;

Q suck q put.

There was no obvious change in the temperature of the solution.

The change in heat during solute dissolution can be measured with an instrument.