High school chemistry questions, behavior of substances in aqueous solutions

After dilution of acetic acid with water, its concentration decreases, the acidity of the solution decreases, and the pH increases. After adding sodium acetate crystals, the concentration of acetate ions in the solution increases, and due to the homoionic effect, the ionization equilibrium of the original acetic acid molecules moves to the direction of the reverse reaction (inhibits ionization), the concentration of hydrogen ions decreases, and the pH also increases.

b.Dilution with water promotes the ionization of acetic acid molecules, while sodium acetate crystals inhibit acetic acid ionization for reasons as described in item a.

c.The dilution of acetic acid with water undoubtedly reduces the ion concentration, so that the conductivity of the solution is weakened; After adding sodium acetate crystals, the ion concentration in the solution increases, and the conductivity will be enhanced.

d.See option A. Since the ion volume of water remains unchanged at constant temperature, when the concentration of hydrogen ions decreases, the concentration of hydroxide ions must increase.

To slow down the reaction rate, i.e., to reduce the concentration of hydrogen ions in solution; And because it does not affect the total amount of hydrogen generated, the added substance cannot react with the hydrogen ions in the original solution to form other substances leaving the system.

It reacts with HCl to form water, which consumes hydrogen ions and reduces the total amount of hydrogen produced.

b.Same as a.

c.You don't give a state of matter, so you can't choose this option. If the sign of (aq) is given in the question, that is, sodium sulfate solution is added, although there is no chemical reaction, it plays the role of diluting the solution, which is the same as simply adding water, so that the concentration of hydrogen ions decreases, but the total amount does not change, which can meet the requirements of the question; But if it is (s), i.e., solid, it does not have this effect.

d.After adding sodium acetate crystals, acetate will immediately combine with hydrogen ions in the solution to form a weak electrolyte acetic acid, which reduces the concentration of hydrogen ions in the solution and slows down the reaction rate. However, acetic acid still has an ionization equilibrium, and as the free hydrogen ions in the solution continue to turn into hydrogen gas and escape out of the solution, the ionization balance of acetic acid is also constantly shifting to the right until finally all the hydrogen ions can be released, and the amount of hydrogen produced will not be affected.

2naoh+co2=na2co3+h2o

Sodium (Na) reacts with water (when reacting with water, a beaker should be applied and a glass sheet should be covered on the beaker, and during the reaction, the sodium block floats on the water surface, melts into a ball, swims on the water surface, has a "hiss" sound, and there is a splash of products), generates a strong alkaline NaOH solution, and releases hydrogen. In solid NaOH, OH is covalently bonded with O-H, and NA and OH are bound with strong ionic bonds, and its dissociation degree is nearly 100% when dissolved in water, so its aqueous solution is strongly alkaline, which can make the colorless phenolphthalein test solution turn red, or make the pH test paper, purple litmus solution, etc. turn blue.

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 soluble in water are -OH, -CHO, -COOH, -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 influence of hydrophilic groups and hydrophobic groups on solubility is about the same, 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- is a hydrophilic group).

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.Poorly soluble in water, and less dense than water, organic matter, in the upper layer.

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.Poorly soluble in water, and denser than water, organic matter in the lower layer.

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

This topic is ruthless enough, then I will summarize it, there is no way to do it Metals and reactions, active metals such as: a a high temperature It is worth noting that e e inference is used on acidic and alkaline oxides and alkali metal peroxides, superoxides and reactions:

a a a a a reacts with water and dilute acids to produce and is rarely used reacts with halogens: cl cl cl , note that there is another very important reaction here:

a r a r crystallizes with some substances: u u carbon group and reaction:

a a( i a a i nitrogen group and reaction: or one that needs to be memorized:

g g ( is the reversible reaction of weak acid and base hydrolysis: cl cl

Electrolysis: ACL A Cl with unsaturated hydrocarbons or derivatives of hydrocarbons:

As et al react with halobenzene substitution under the condition of a to produce phenol and hydrohalic acid and in the case of chloroplasts and light:

There is also a very important one in organic, a a can use this to judge the strength of acidity, that is, the principle of strong acid to weak acid! Almost, what I wrote is representative, in fact, there are some things you can try to summarize by yourself, I can contribute, you have to study hard!

1.Active metals (sodium and before sodium) can react directly with cold water to form alkali and hydrogen, and after magnesium and aluminum (zinc, iron, tin, lead) at high temperatures, react with water vapor to form oxides and hydrogen.

3.Soluble acids and bases can react with water to form corresponding acids or bases such as sulfuric acid soluble, SO3 + H2O = H2SO4

4.Peroxides react with water to form alkali and oxygen.

5.The carbides of the active metal react with water to form alkalis and organic hydrocarbons (different substances, different hydrocarbons) Cac2+H2O=C2H2+Ca(OH)26Hydrolysis of salts (content of the second year of high school).

7.Hydrolysis reaction:

Hydrolysis of esters. Hydrolysis of halogenated hydrocarbons (high sophomore content).

8.Halogen elementals react with water.

2f2+2h2o=4hf+o2,x2+h2o=hx+hxo(x=cl\br、i)

1) Al2, Mg3, NH42, H2, SO4 8 units: mol

2)a=1 b=7 c=9

3) There may also be k, test method: flame color reflection.

It can be obtained according to the final precipitate amount mg. The maximum precipitation is minus magnesium to obtain aluminum. The flatness of the precipitation curve is due to the presence of ammonia, which is 4m for oxygen and 2m for ammonia according to 8m of sodium peroxide.

From this, it can be seen that b is 7, and from the precipitation curve, we can know that b-a=6, a=1, and c is the amount of dissolved and precipitated is 9Because the charge needs to be conserved and can only be sulfate of 8The undetermined ion is the potassium ion.

Analysis: Looking at the precipitation curve first, sodium hydroxide is produced by adding sodium peroxide, but there is no precipitation at the beginning, indicating the presence of hydrogen ions in the solution. The magnesium hydroxide and aluminum hydroxide precipitates produced between A and B, and the sodium peroxide is added continuously, and the precipitate is not immediately dissolved, indicating that there are ammonium ions in the solution, and the precipitate begins to dissolve when the ammonium ions are completely converted into ammonia.

Then analyze the gas curve, the oxygen that is produced at the beginning, then the oxygen and ammonia are produced, and when the ammonia is completely released, only oxygen is produced.

1.h+ magnesium ion, aluminum ion, ammonium ion, sulfate 2 3 2 2 greater than or equal to 8b=7 c=9

3.May contain potassium ions, which can be used to reflect firmness in a flame color.

I only wrote so much first, and if you don't understand something, please ask.

H ion: Al ion, NH4 ion, Mg ion, SO4 ion.

a=1 b= 7 c= 9

A small amount of the solution is dipped in a clean platinum wire, burned on the flame of an alcohol lamp, and the color of the flame is observed through the blue cobalt glass, and if the flame is purple, it contains potassium ions.

You're too careless to study, aren't you? Such a basic question will not be!

ML take 10ml and consume 20ml of HCL! Then 100ml consumes 200ml, that is, HCL is consumed! BA is 1 with HCL

2 relationships! Zeke's sample is !! Then the mass fraction of 1mol of Ba(OH)2·NH2O is 350!

350 minus BA(OH)2 doesn't make all three answers come out!!

Study hard!!

It's very simple, one of the four solutions is an alkaline solution. An acid solution, a salt solution, an alkaline chromogenic agent.

1. Find a group of two pairs of combinations to have a chromogenic reaction, which are NaOH solution and phenolphthalein (;

2. Add the other two unknown solutions respectively, and always find the one that makes the color development reflection fade is HCl, and the one that adds the reagent to reflect no change in the color development is NaCl solution;

3. Drop three drops of confirmed HCl into a small amount of NaOH solution and phenolphthalein (in, in the solution of adding mixed reagents to unknown solutions respectively, if the drops are dropped into the fourth lowest, the obvious color reaction is NaOH solution, and the other is phenolphthalein (.

AI I've forgotten it, I miss chemistry so much. Study chemistry well, memorize more, do more questions, review more, and have more rules.

Weak electrolytes are generated, gases, precipitates, do not coexist in solution; If there is a redox reaction, it does not coexist in solution; The dihydrolyzed ones do not coexist in solution.

Ions that can be dihydrolyzed with each other, hydrogen ions, carbonate and bicarbonate, etc.

1.Active metals (sodium and pre-sodium) react directly with cold water to form alkali and hydrogen.

Before, magnesium and aluminum (beauty) after (zinc, iron, tin, lead) at high temperatures with water vapor.

The reaction produces oxides and hydrogen.

3.Soluble acids and bases corresponding to oxides of the same valence state can react with water to seep and leak into the corresponding acids or bases.

For example, sulfuric acid is soluble, SO3 + H2O = H2SO4

4.Peroxide.

It can react with water to form alkali and oxygen.

5.The carbides of the active metal react with water to form alkalis and organic hydrocarbons (different substances, different hydrocarbons) Cac2+H2O=C2H2+Ca(OH)26Hydrolysis of salt reflux (content of the second year of high school).

7.Hydrolysis reaction:

Hydrolysis of esters. Hydrolysis of halogenated hydrocarbons (high sophomore content).

8.Halogen elementals react with water.

2f2+2h2o=4hf+o2,x2+h2o=hx+hxo(x=cl\br、i)

The answer is d.

Iron ions are equivalent to catalysts in this reaction, after SO2 is passed into the solution, because the reduction of SO2 is stronger than Fe2+, Fe3+ will react with SO2 to form Fe2+ and substances containing +6 valence sulfur elements, and because of the white precipitate formed after dropping into the barium chloride solution, it can be seen that the substances containing +6 valent sulfur elements are sulfuric acid, so the solution will turn light green. Since sulfuric acid is a strong acid, its hydrogen ions and the nitrate originally contained in the system are added together, which is equivalent to containing nitric acid, which will oxidize the Fe2+ generated by the reaction just now and turn it back to Fe3+, then this reaction can be regarded as a redox reaction between NO3- and SO2, and it is NO3- ions that are reduced.