The problem of chemical solubility, the relationship between solubility and solubility

Whether to write the precipitation symbol or not has nothing to do with the solubility of the substance, if there is a precipitation, write the precipitation symbol, the magnesium carbonate is generated because it forms a precipitate in the solution, even if the soluble substance is saturated and precipitated, it is also necessary to write the precipitation symbol, for example, in the ammonia industry, the soluble sodium bicarbonate has a reaction formula and the precipitation symbol is also written. And if calcium oxide forms a precipitate with water, it is also to be written. As for your exam requirements, you don't need to know so much, you only need to remember a few to write or not to write, the reactants in the equation do not write the precipitation symbol, the product in junior high school to write the precipitation symbol in addition to calcium hydroxide in the solubility table, so calcium sulfate, silver sulfate should also be written, there will be no equation I said not to write the precipitation symbol in the high school entrance examination, but it will not be in high school in the future, and calcium hydroxide, you only need to remember the reaction of calcium oxide and water to produce slightly soluble calcium hydroxide without writing, Others depend on the situation, if the title says that calcium hydroxide precipitation is generated, you need to write, if you don't say it, you don't need to write.

It's not easy to remember these things when you're in high school, so choose me

Whether to write or not to write the precipitation symbol is based on the solubility of the reactants. Because you're still in junior high school, you don't have much chemistry to learn too much, so you can't stick to the solubility table at the back of the book. Actually, I didn't even take a good look at it back then, hehe.

Like you gave the first example, because the generated MgCO3 is very small relative to the solubility of the reactants, so there is precipitation after the reaction. In the second example, the two are basically not reacting.

Knowledge should be learned, hehe, I hope it will help you.

When slightly soluble, the solubility is very small, and most of the product will precipitate due to reaching a saturated state.

Calcium hydroxide becomes turbid in water for a short time, and no precipitation can be observed. But when the amount is very large, there will be the same.

It's just a long-term habit, rote memorization.

Solubility refers to the magnitude of the solubility of a substance, which is the physical property of the substance; Solubility is a measure of the solubility of a substance, and it is a quantitative analysis of the strength of the solubility of a substance. So the solubility of a substance is described in terms of solubility.

Under special conditions, more solute is dissolved in the solution than normal, and it becomes a supersaturated solution. The maximum amount of solute that can be dissolved in a solvent (and sometimes a solution) per serving (usually per mass) is the "solubility of the solute in this solvent".

The highest amount of a substance dissolved in a certain amount of solvent at a certain temperature and pressure. It is generally expressed in grams of dissolvable substances in 100 grams of solvent. The solubility of a substance in a certain solvent is mainly determined by the properties of the solvent and the solute, that is, the dissolution equilibrium constant of the solute in the solvent.

For example, water is the most common and commonly used solvent, and methanol and ethanol can be miscible with water in any ratio. Most alkali metal salts are soluble in water; Benzene is almost insoluble in water.

Solubility refers to the ability of a substance to dissolve in a solvent.

Solubility is determined by the solubility of a substance at 20 hours.

Solid) insoluble (insoluble) slightly soluble soluble soluble soluble 20) 10g

Solubility is a measure of the solubility of a substance;

Solubility, the mass dissolved by a solid substance when it reaches saturation in 100g of solvent at a certain temperature, is called the solubility of the substance in this solvent.

Solubility is a physical property of a substance when it forms a solution. It refers to a property of the solubility of a substance in a specific solvent. Solubility refers to the maximum amount of solute that a solution that reaches (chemical) equilibrium cannot hold more solutes, and refers to the maximum amount of dissolution of a substance in a particular solvent.

Under special conditions, more solutes will be dissolved in the solution than normal, and it will become a supersaturated solution.

1.It refers to the solubility of a substance in a solvent.

2.Solubility is a physical property, and most dissolution is a physical change (some dissolution is a chemical change, such as soda dissolved in an acid and a chemical reaction occurred).

3.Solubility is determined by the solubility of a substance at 20 o'clock.

More than 10 grams is soluble, more than less than 10 grams is soluble, more than less than grams is slightly soluble, and less than one gram is insoluble.

What is the relationship between solubility and solubility?

Solubility is the nature and solubility is the number.

Solubility refers to the ability of a substance to dissolve in a solvent.

Solubility is determined by the solubility of a substance at 20 hours.

Solid) Insoluble (insoluble) Slightly soluble Soluble Soluble (20) 1g 10g >10g

Solubility is a measure of the size of a substance's solubility capacity;

Solubility, the mass dissolved by a solid substance when it reaches saturation in 100g of solvent at a certain temperature, is called the solubility of the substance in this solvent.

Solubility; The question of how much to dissolve.

Solubility; Problems with the nature of dissolution.

There is both a connection and a difference between the solubility of the two concepts of a substance and the solubility of a substance. The solubility of a substance, i.e., the magnitude of the dissolving capacity of a substance. This ability depends both on the nature of the solute and on its relationship with the solvent.

No matter how complex the cause or the factors affecting the solubility of a substance may be, it can simply be understood that it is a property of the substance itself. For example, table salt dissolves easily in water, but it is difficult to dissolve in gasoline. Grease is easily soluble in gasoline, but difficult to dissolve in water, etc. This property of salt and oil is an inherent property of itself, which can be summarized by the concept of solubility.

However, solubility is different, it is a "ruler" to measure the solubility of a substance according to the standards prescribed by people. Under the same specified conditions, different solutes can be dissolved in the same solvent in different quantities, which objectively reflect the difference in their solubility. Therefore, the concept of solubility not only contains the meaning of the solubility of substances, but also further reflects the specific quantity under specified conditions, which is the concretization and quantification of solubility, and is a concept formed after making provisions for the quantitative study of the solubility of various substances.

I don't think solubility is the mass dissolved by a solid substance when it reaches saturation in 100g of solvent at a certain temperature, and it is related to the solute, the solution, and the temperature. So the first sentence is not quite accurate. 2.

The chemical reaction between the substance and water has an impact on the solubility of the substance for a short time, such as quicklime dissolved in water and reacts with water, releasing heat and reducing solubility.

First, the principle of similarity and dissolution.

1. Polar solvents (such as water) are easy to dissolve polar substances (polar substances in ionic crystals, molecular crystals, such as strong acids, etc.);

2. Non-polar solvents (such as benzene, gasoline, carbon tetrachloride, alcohol, etc.) can dissolve non-polar substances (most organic matter, BR2, I2, etc.);

3. Substances containing the same functional groups are miscible with each other, such as hydroxyl (-OH) in water, which can dissolve alcohols, phenols and carboxylic acids containing hydroxyl groups.

2. Solubility of organic matter and solubility of functional groups.

1 Solubility of functional groups:

1) The functional groups (i.e., hydrophilic groups) that are easily soluble in water are -OH, -CHO, -COOH, and -NH2.

2) The functional groups (i.e., hydrophobic groups) that are insoluble in water are: all hydrocarbon groups (—CNH2N+1, —CH=CH2, —C6H5, etc.), halogen atoms (—X), nitro groups (—NO2), etc.

2 The ratio of hydrophilic groups to hydrophobic groups in a molecule affects the solubility of substances:

1) When the number of functional groups is the same, the solubility gradually decreases with the increase of the number of carbon atoms of hydrocarbon groups (hydrophobic groups).

For example, solubility: CH3OH>C2H5OH>C3H7OH>......In general, alcohols with a carbon number greater than 5 are insoluble in water.

2) When the number of carbon atoms in the hydrocarbon group is the same, the greater the number of hydrophilic groups, the greater the solubility of the substance;

For example, solubility: CH3CH2CH2OH (3) When the hydrophilic group and the hydrophobic group have about the same effect on solubility, the substance is slightly soluble in water;

For example, common substances that are slightly soluble in water are: phenol C6H5-OH, aniline C6H5-NH2, benzoic acid C6H5-Cooh, n-pentanol CH3CH2CH2CH2CH2-OH (in the structure of the above substances, the "-" on the left is a hydrophobic group, and the right is a hydrophilic group); Ethyl acetate CH3COOCH2CH3 (where —CH3 and —CH2CH3 are hydrophobic groups, and —COO- are hydrophilic groups).

4) A substance composed of two hydrophobic groups must be insoluble in water.

For example, the halogenated hydrocarbon R-X and the nitro compound R-NO2 are insoluble in water because the hydrocarbon group R-, halogen atom-X and nitro-NO2 are all hydrophobic groups.

3. Density of liquid organic matter.

1.Organic matter that is insoluble in water and has a density less than water.

For example, liquid hydrocarbons (homologues of ethane, ethylene, benzene, benzene......Liquid esters (ethyl acetate, glyceryl stearate, ......Monochlorohaloalkanes (1-chloroethane......Petroleum products (gasoline, kerosene, grease, ......）

Note: Gasoline products are divided into straight-run gasoline and cracked gasoline (containing unsaturated hydrocarbons).

2.Organic matter that is insoluble in water and has a density greater than that of water.

Examples: carbon tetrachloride, chloroform, bromobenzene, carbon disulfide.