Some physical chemistry questions up to 100 points .

1.Water usually freezes at zero degrees Celsius. However, water can remain liquid even below zero degrees Celsius, which is called supercooled water.

When the supercooled water reaches below the critical point, two states are separated, namely low-density water and high-density water. Correspondingly, there are also two types of amorphous ice, low-density and high-density. Because water tends to freeze at low temperatures, and because there is no existing theory of the transfer of amorphous ices to each other, there is a lot of controversy about the amorphous diversity of water.

One of them is whether there will be a continuous transfer of amorphous water in two densities.

2.This phenomenon is actually what physics calls the "capillary phenomenon".

When we talk about "capillaries", we need to talk about the words "infiltration" and "non-infiltration".

A drop of mercury placed on the glass is able to roll around without attaching to it, a phenomenon called "non-wetting", and for glass, mercury does not infiltrate the liquid

A drop of water placed on top of the glass will adhere to the glass to form a thin layer, a phenomenon called "infiltration".

In the case of glass, water is an infiltrating liquid

The same zinc liquid is wetted with some solids, but not with some solids, such as water can infiltrate glass but not paraffin Mercury cannot infiltrate glass, but can infiltrate zinc

The phenomenon of wetting and non-wetting is the manifestation of the action of molecular forces When the liquid is in contact with the solid, a thin layer of liquid is formed at the contact point, which is called the attachment layer The molecules in the attachment layer are attracted by both the solid molecules and the molecules inside the liquid If the attraction of the solid molecules is relatively weak, the hungry molecules in the attachment layer are sparse than the inside of the liquid, and there is a contraction force similar to the surface tension in the attachment layer At this time, the liquid surface in contact with the solid has a tendency to shrink Forming a non-wetting phenomenon On the contrary, If the attraction of solid molecules is quite strong, the force of liquid repulsion in the adhesion layer will appear, and the surface of the liquid in contact with the solid will have a tendency to widen, forming an infiltration phenomenon

Hold water in a glass container and bend upwards because the liquid side near the glass wall does not soak the glass because the mercury does not soak The liquid side near the glass wall bends downwards because the mercury does not soak into the glass wall

The phenomenon of the infiltrated liquid rising in the thin tube and the phenomenon of the non-infiltrating liquid falling in the thin tube is called the capillary phenomenon, and the tube that can release the capillary phenomenon is called the capillary

3.I don't know.

4.It's inevitable, maybe it's not clean, or maybe the Earth's gravity isn't strong enough.

1 Because there is a small amount of air dissolved in the water, the air in the water only occupies the space between the water molecules in the liquid state, and after freezing, Anli said that the air in the water will be forced to the outside, but the water freezes first, and the air in the original water is left inside, but it actually exists to occupy a certain space, so its volume will be larger than the original. For example, if you pour 1 liter of water into 1 liter of alcohol, their volume is not equal to 2 liters.

2 Because there is a gravitational pull between the molecules.

3 It does not react, but the fire needs oxygen to burn, so the fire will be extinguished.

4 This is the same principle as question 2.

5 This is due to the fact that neon lights are loaded with noble gases, and different noble gases will have different colors under the action of high temperatures after being electrified.

6 This question is very correct, you don't need to be there!

7 Today's displays are arranged by controlling the arrangement of small pixels on the screen one by one and then forming a pattern.

8 Melting point of oxygen: -180 Fixed point of oxygen: -218 Melting point of carbon dioxide Fixed point of carbon dioxide:

9 This is not clear!!

1。You mean that the change of water into ice is a phenomenon of increasing volume, when water (generally at 4 degrees Celsius) is in a liquid state, its density is 1. In the solid state (zero degrees), however, its density is .

This is why it has the characteristics of cold expansion and heat contraction. In other words, the density in the solid state is smaller than in the liquid state. This is because it produces crystals at the time of solidity, so that a certain space is created between its molecules.

With the same mass of water, when it becomes less dense ice, the volume of course becomes correspondingly larger.

2。The surface tension of water, as long as the mouth of the container is higher than the liquid level, is concave.

The surface tension of water is small, and it has a wetting effect on the outside world.

When measuring the liquid, the water will wet the wall of the container, and the liquid level will be concave, but there is no need to worry, as long as the concave liquid level prevails when measuring

To add one more thing, mercury is also a liquid, but it has a lot of surface tension, so there is a convex liquid surface in the container. And the water droplets we usually see fall to the ground and scatter and not drip, but the mercury is dripping, which is also the effect of his surface tension!

3。There should be no reaction, the reaction between nitrogen and oxygen requires temperature and catalyst, and under natural conditions, nitrogen can only react with oxygen under lightning conditions.

4。On the one hand, because water is viscous, on the other hand, the surface of the cup is very hydrophilic, and the water adheres well to it. In other words, the "sticking" of water molecules on the surface of the glass is conducive to reducing the surface energy of the whole system.

If there is a strong hydrophobic material on the surface of the cup, such as the kind of paint that does not stick to the pan, it is easy to pour it clean in one go.

5。Neon lights work: when the electrons of a noble gas in an excited state transition to the ground state, photons are emitted, forming colorful light.

6。The principle of electrolysis of water: H2O is composed of H element and O element, and the O element on the anode loses electrons, and the valency increases, forming O2; The H element on the cathode gains electrons, and the valency decreases, resulting in H2

7。The working principle of the display: the liquid crystal display and the plasma display are similar in principle, through the small pixels on the screen are controlled one by one, and finally put together the whole picture, and the rear projection is similar to the cathode ray tube display.

There are also the latest e-ink displays, which do not need to be powered on all the time when in use, and only consume a small amount of power when the image changes.

8。Melting and freezing points of oxygen: -180 degrees Celsius -218 degrees Celsius.

Melting and freezing point of carbon dioxide: Celsius Celsius.

9。You will know the answer by referring to this.

1. 10 GnaOH in 100g of NaOH solution with mass fraction of 10, 90g

H20,1) Add NaOH solid X to the solution set to 10

g,(10+x) (10+x)+90=20%The solution is:x=

Evaporated water YG10 100-Y

Solution: y=50g

（2）ca（oh）2

3) Enlargement.

Calcium bicarbonate, magnesium bicarbonate and calcium hydroxide have been excluded from the sample, as well as: barium carbonate, calcium carbonate, magnesium hydroxide to be tested.

The added mass of 20g in the d bottle is the mass of the substances in the sample to react to form carbon dioxide, and all three substances can react with dilute sulfuric acid, but only barium carbonate and calcium carbonate react with dilute sulfuric acid to form carbon dioxide.

Using the limit method: assuming that the sample is all barium carbonate:

baco3+2h+=ba2++co2↑+h2o197g...44g50g...m1m1=20g*44g/197g=

However, the sample produces a total of 20 g of carbon dioxide, so it is not possible to contain only barium carbonate, assuming that the sample contains only calcium carbonate.

caco3+2h+=ca2++co2↑+h2o100...44g50g...m2m2=44g*50g/100g=22g

22g＞20g

It is not possible to have only calcium carbonate in the sample, but it certainly contains calcium carbonate.

So there are three possibilities for the composition of the x-matter:

Calcium carbonate + barium carbonate.

Calcium carbonate + magnesium hydroxide.

Calcium carbonate + barium carbonate + magnesium hydroxide.

[Design and implementation plan].

2) Student A put a small amount of ground X substance in the beaker, add enough distilled water and stir it thoroughly, and let it stand to take it.

The layer clear solution was dropped into the Na2CO3 solution, and there was no white precipitate, indicating that there was no Ca(OH)2 in the X substance

Evaluation] 1) The NaOH solution in bottle A absorbs carbon dioxide from the air If there is no NaOH solution in bottle A, the mass in bottle D will remain unchanged.

2) The possible composition of the analyzed X substance is Mg(OH)2+CaCO3 or CaCO3+BaCO3

caco3+h2so4=caso4+h2o+co2↑

50---x

100：:44=50：x

x=44*50/100=22

baco3+h2so4=baso4+h2o+co2↑

50---x

100：:44=50：x

x=44*50/193=

50 g of CaCO3 reacts with H2SO4 to produce 22 g of CO2 and actually produces 20 g of CO2, while Mg(OH)2 reacts with H2SO4 not to produce CO2, and 50 g of BaCO3 reacts with H2SO4 to produce CO2 g, so X must be a mixture of Mg(OH)2 with CaCO3 or CaCO3 with BaCO3.

Substance X may consist of 1 or 2 or 3 of Mg(OH)2, CaCO3, BaCO3

The CaCO3 mass or BaCO3 mass required to generate 20g CO2 was calculated respectively

caco3(100) -co2(44) ,m(caco3)=20/44*100= ;

baco3(197) -co2(44) ,m(baco3)=20/44*197= 。

Discussion: (1) It is impossible to have only BAC3 without CAC3, because it is necessary to produce 20 g of CO2, which exceeds 50 g.

2) It is possible to be composed of CaCO3 and Mg(OH)2: g CaCO3 and G= Mg(OH)2

3) When CaCO3 and BaCO3 are present at the same time, 20 g CO2 is produced, and the total mass range of CaCO3 and BaCO3 is Mg(OH)2 when the total mass of CaCO3 and BaCO3 is less than 50 g.

When the total mass of CaCO3 and BaCO3 is equal to 50 g, these two carbonates are used.

When the total mass of CaCO3 and BaCO3 is greater than 50g, it is not possible to exceed 50g.

Conclusion (3 possible scenarios):

caco3、mg(oh)2；

caco3、baco3、mg(oh)2；

caco3、baco3

1.The stability and melting point of a substance are not necessarily related to the type of valence bond, as there are often many different types of bonds for the same substance.

The melting and boiling point mainly depends on the type of crystal of the substance, generally speaking, atomic crystals, ionic crystals, and molecular crystals.

2.The solubility of NaHCO3 is less than that of Na2CO3, the former is more susceptible to acid reaction, and the latter is more stable.

Solubility can't be explained, but you can keep in mind that bicarbonate of intolerant carbonate is soluble relative to that carbonate (e.g., CaCO3) and bicarbonate of receptive carbonate is insoluble relative to that carbonate (e.g., Na2CO3).

The former is easier to react with acids because Na2CO3 reacts with acids in essence: Na2CO3 reacts with acids first to form NaHCO3

The latter is stable because NaHCO3 is thermally decomposed to form Na2CO3, CO2 and water.

3.For a certain amount of gas, according to PV=NRT, under the condition that the pressure (p) and temperature (t) are unchanged (r is constant), the density increases, the volume (v) increases, the amount of matter (n) increases, and the molecular weight increases.

Regarding color, it is necessary to analyze the specific problem on a case-by-case basis. If there is no reaction inside the gas, then the color is darkened, and if there is a reaction (e.g. NO2=N2O4), it is not necessarily.

4.There are two main organic reactions in which bromine is involved in high school: the addition of bromine to olefins (with bromine water) and the substitution of bromine on the benzene ring (with liquid bromine), not necessarily with liquid bromine. In addition, bromine can also be used as a haloalkane, using liquid bromine.

5.There is no clear requirement for the temperature of the silver mirror reaction water bath, which is about 80-90 degrees. The water bath is designed to prevent the water from boiling and to speed up the reaction rate.

1.It is determined by the strength of the bond energy. It can be judged by the size of the particle radius. The smaller the particle radius, the greater the bond energy, the more stable the substance formed, and the higher the melting and boiling point.

High solubility (by measuring the solubility of both at the same temperature.) It can also be found in the solubility table). Na2CO3 is easy to react with acid (the degree of hydrolysis of Na2CO3 is greater than that of NaHCO3, and the alkalinity of its aqueous solution is strong, so Na2CO3 is easier to react with acid), and Na2CO3 is more stable (NaHCO3 should be decomposed by heat to form Na2CO3).

3.If the value is measured at the same temperature and pressure, then its density is proportional to the molecular weight. If the gas has a color, the color will generally deepen when the volume is reduced.

4.The addition reaction of unsaturated bonds can be done with bromine water. The oxidation reaction of the aldehyde group can also be done with bromine water. The substitution reaction of phenol and bromine is also done with bromine water. Liquid bromine is used for the bromination reaction of benzene.

5.The silver mirror reaction does not have a clear requirement for the water bath temperature. Generally, it should not be too high, because the temperature is too high, and the fluidity of water is enhanced, which is not conducive to the precipitation of elemental silver on the inner wall of the test tube. The role of the water bath is to provide a stable temperature. And it's easy to control the temperature.