Can anyone help me with these three chemistry problems

1.When disinfecting the surface with alcohol cotton balls, why does it make people feel a little cool!

Under normal circumstances, there is no water on the surface, but after using a cotton ball, the alcohol is sucked on the **, and then volatilized, and the volatilization needs to absorb heat.

2.Coastal areas generally have cooler summer temperatures than inland areas Why?

There is more water around the coastal area, the specific heat of the water is much greater than the specific heat of the sand and gravel soil on the land, and in summer, the heat in the air will be absorbed by the water, because the specific heat is relatively large, so the water does not heat up much, so that the surrounding temperature is relatively low.

In winter, the opposite is true, with warmer temperatures in coastal areas than inland. It is also because of the specific heat of water.

It's a matter of physics.

Alcohol cotton ball rubs the body, the alcohol is easy to evaporate, vaporizes and absorbs the heat, and feels cool.

The specific heat of water is large, much larger than that of rock, so the temperature does not rise or decrease easily, although the heat energy received is the same. There is a lot of water vapor in the air in the coastal areas, which absorb a lot of heat but do not raise a lot of temperature. As a result, the temperature is lower in coastal areas than in inland areas.

1.Exactly volatilization takes away the heat.

2.Water molecules in the air take away the heat.

1.Ethanol evaporates and absorbs heat from the surface.

2.The heat capacity of seawater is greater than that of land, and the seashore at the same latitude is slightly cooler than inland.

1. Alcohol evaporates like water and absorbs heat.

2. It is related to the specific heat capacity of water and the specific heat capacity of buildings such as stones, and the specific heat capacity of water is the largest under the same conditions, so the temperature in coastal areas in summer is generally lower than that in inland areas.

Standard parsing.

What you are talking about is (ice pack reaction) according to high school textbook Elective 2 to explain endothermic reaction and exothermic reaction, ice pack reaction.

Mix with barium hydroxide octahydrate and ammonium chloride solids.

Make ice packs. **Refrigeration principle: barium hydroxide octahydrate and ammonium chloride react to produce barium chloride.

Ammonia and water. Since the solubility of ammonia is 1:700

So the ammonia gas dissolves in the resulting water.

Ammonia monohydrate is formed.

That's what you get with the liquid.

NOTE: This is a typical endothermic reaction in high school textbooks.

The college entrance examination must be mastered.

Commonly found in multiple-choice questions.

Judgment of thermal effects.

(1) The conditions of the first question are incorrect. It should be a 5mol, b 5mol2h2+o2*****====2h2o2

Water is liquid at room temperature at 15mol, and the remaining gas after the reaction is.

So its maximum density is 80g 20l=

Choose B(2)CO2C

h2o~~~2h

Therefore, in the volume of hydrocarbons, the ratio of the number of c atoms to h atoms is: 1, so the three compounds of c(3) can be regarded as c6h8 and c2h2h2o

C8H8 regards the second compound as the combination of C2H2 and 'water molecule', then the ratio of the number of C atoms to H atoms is 1:1, so its mass ratio is 12:1, then the mass fraction of H element is 72% 12=6% and the rest is the mass fraction of the 'water molecule' of the second compound, W(H2O)=1-72%-6%=22%, then the mass fraction of oxygen element is 16 18 22%=so choose B(4)A:

O2B:CC:H2

a：co2b：h2o

c：ch4d：cob+d:

co+h2o*****=hcooh

1,4/40=

Because the solution of H2O with Na+DE.

The amount of matter. The ratio is 20:1, so the amount of water = 20 * solute mass fraction.

2. Set a mixture of K2O2 and Ko2.

The amount of matter. x, y, respectively

2x+y)39:(2x+2y)*16=13:8x:y=1:2

3. Set the alloy in the magnesium iron.

The amount of matter. x, y, respectively

24x+56y=

x+y=x=,y=

So the mass of magnesium is:

Number of iron atoms =

Oxygen required for hydrogen combustion.

The volume of air is.

4, a:b: density ratio =:16

In the reaction between zinc and dilute nitric acid, nitric acid has two effects: acidic action and oxygen difference sonorization, and the nitric acid that plays an acidic role exists in the form of Zn(NO3)2, and this part of nitric acid is not reduced;

The oxidizing nitric acid is reduced and exists in the form of the reduction product N2O, the number of electrons lost in zinc is equal to the number of electrons in the nitric acid, the ratio of the amount of the substance is 2:5 of zinc reacts with dilute nitric acid: 2Zn + 5Hno3 2Zn(NO3)2+ N2O, the ratio of the amount of reduced nitric acid to the amount of nitric acid that has not been reduced is 1:

4 。Key points: The acidity and oxidation of oxidizing acids, and the acidity and reduction of reducing acids are common knowledge points for redox reactions.

Let 2molZn participate in the reaction, because there is no Zn left, then 2molZn(NO3)2 is finally generated, which obviously contains 4molNO3, which is not involved in the redox reaction, according to the conservation of gain and loss electrons: 2 N(Zn)=N(HNO3) 4, then N(HNO3)=1mol, that is, 1mol Hno3 is reduced.

Equation: 4zn+10hno3 4zn(no3)3+n2o +5h2o

Reverted: Not Reverted = 1:4

In the reaction between zinc and dilute nitric acid, nitric acid has two effects: acidic and oxidative, the nitric acid that plays an acidic role exists in the form of Zn(NO3)2, and the nitric acid of the round car has not been returned to the orange; The oxidizing nitric acid is reduced in the form of the reduction product N2O, the number of electrons lost in zinc is equal to the number of electrons obtained in nitric acid, and the ratio of the amount of matter is 2:5 zinc reacts vertically with dilute nitric acid

2zn+5hno3 2zn(NO3)2+ N2O, the ratio of the amount of reduced nitric acid to the amount of unreduced nitric acid is 1:4.