A few chemistry questions with an additional reward

1.If it is concentrated hydrochloric acid, there will be a white mist on the mouth of the bottle when the cap is opened, otherwise it is not concentrated hydrochloric acid.

2.Take a small amount of solid to be measured, add a small amount of dilute hydrochloric acid, if there is gas generation, it contains sodium carbonate, if there is no gas generation, it does not contain sodium carbonate.

Copper oxide 2HCl+CuO=CuCl2+H2O was added to hydrochloric acid, and the acidity weakened and the pH increased.

Carbon dioxide gas is introduced into the water CO2 + H2O = H2CO3 to form carbonic acid and the pH decreases.

Concentrated hydrochloric acid is added to dilute hydrochloric acid, and the acidity is enhanced and the pH is reduced.

Hydrochloric acid solution NaOH + HCl = NaCl + H2O was added dropwise to the sodium hydroxide solution, and the alkalinity became weaker and the pH decreased.

1.Open the lid and see if there is any white mist.

2.Take a sample, add clarified lime water to it, see if there is a white precipitate, if there is... If not, then ...

1.Density can be measured.

2.Aqueous solution + hydrochloric acid.

1.Open the lid and see if there is a white mist, and if there is, yes. If you don't, you don't.

2.Dissolve first, and then add HCl drop by drop to see if there is gas generation immediately, and the gas immediately contains sodium bicarbonate, and after a while, the gas is sodium carbonate.

1.Open the lid and see if there is smoke coming out, or thick hclIf you don't, you don't.

2.Take the sample in a test tube, add a small amount of HCl, and there are bubbles with Na2CO3bar.

Because the density of A relative to H2 is 29

Therefore, the positive amount of molar celestial is m(a)=29x2=58(g mol)m(CO2)=

What is rotten is n(a):n(c)=1:3

So the number c in a is 3

58-3x12=22

Because 22 = 16 + 6

So the molecular formula: C3H6O

Molar mass scrutiny m = 58g mol is generated.

So there are 3 C's in A

The remaining 58-36 = 22 = 1 o + 6 h

So A is Kizakura C3H6O

The reaction with silver ammonia solution shows that there is an aldehyde group, and the junction is broad-fronted: C2H5-CHO is acetaldehyde.

The molar mass m(a) = 29x2 = 58 (g mol) is.

Generate implicit judgments. So there are 3 C's in A

The remaining 58-36 = 22 = 1 o + 6 h

So A is C3H6O

Structural formula: C2H5-CHO is also known as acetaldehyde.

Explanation: By calculating the relative molecular bending mass of the organic matter to 58, the friction combustion produces carbon dioxide, and the reaction with the silver ammonia solution shows that there is an aldehyde group, and then the conclusion is drawn.

1.The law of conservation of oxygen a-b.

2. a+b-c

3. a+c-b

4.c, h, o are all available.

5. h2o

Belonging to oxides:

Belonging to the mixture:1

Belonging to salt: The chemical reaction equation of silica and calcium carbonate: silicon dioxide + calcium carbonate = calcium silicate + carbon dioxide.

The phenomenon that most particles can pass through the gold leaf without changing the original direction of travel, proving that there are very few particles that hit the nucleus, so the size of the nucleus is small.

Phenomenon Due to the repulsion of the same sex, the particles change their original direction, or are ** back, but are not adsorbed. Hence it can be proved that the nucleus of an atom has a positively charged nucleus.

Phenomenon There is a part of the particle is ** back, the particle is a helium nucleus, which is composed of two protons and two neutrons, only the mass of the atomic nucleus is large, the particle is ** back. Hence it can be proved that the nucleus mass is large. It can also be used to prove that the nucleus is positively charged.

It's all good calculation questions, although I have an idea at a glance, I don't know if you're afraid of trouble.

I'll give you the general idea, and you can do it yourself

I was able to familiarize myself with the reflection equation, too.

Ammonia corresponds to C 2

Sulfate ions in mol ammonium sulfate.

Then b-c 2

It is the amount of the remaining aluminium sulphate substance.

al2(so4)3

Let a be xmol

SO4 among them

2 - is 2 3x

Whereas, the amount of Al2(SO4)3 is B-C2. Do you understand this correspondence?

Count it out.

Divide by the concentration of HCl solution. How much mol is it (calculate it myself, I'll set it to xmol first) xmolhcl

Corresponds to xmolh+

xmolh+

Corresponds to xmoloh-

According to nana2o

The equation for the reaction of Na2O2 and H2O corresponds to the three substances, and a range of OH- can be obtained.

The interval satisfying xmol is the correct answer.

3。After the ethanol reflection is complete.

The products are CO2 and H2O

In this question, you don't forget about the reflection of water, it's OK.

Look at the question carefully. It was a closed container, and the last question was about the weight gain of the solids, and finally it was OK to just calculate the mass of the substance that was solid.

Filtration refers to the filtration of liquids from insoluble solids.

aAll are liquids. Don't pretend to be a leak.

b are all soluble in water wheel sensitive. No.

cYes, it is possible to separate sediment and water.

Is it OK to fill in D?

That is. Calcium carbonate and water bar.

A with a separating solution B with a hall rotten crystals.

Of the following mixtures, the keys are made using the method of over-muffling filtration to separate them

a.water and vegetable oils.

b.Table salt and sucrose.

c.Mud water.

d.Barium sulfate and water

Answer CD

,)=1/2li2o(s) △h(

2.Negative electrode. Alkali metals react with water.

508g, <5> power c

1）4li+o2=2li2o

2) The cathode li undergoes a displacement reaction with water 254

Let's look at formula 1 first, the -1 price of Cl in NaCl is already the lowest price of Cl in the normal state, so from A to NaCl is a price reduction, then A to B is an increase price, so the valence of B is greater than A. Looking at formula 2 again, from C to A+B, because the valence rises and falls, the valence of C is between A and B. Therefore, the valency of Lu primary color is BCA from high to low.

If you have any questions, you can ask

reaction, a NaCl, chloride valency decreases. (Because the lowest price of Cl is -1 valence, the valency of chlorine in A is definitely higher than that of chlorine in NaCl).

a b, the chlorination valency must be increased.

So the chlorine element valency a b.

Reaction, C A+B, the valency of C must be between A and B, in order to meet the law that the valence rises and falls.

So a c b.

Answer: B c A

1. The redox reaction must rise and fall.

2. Sodium ions rarely become valent in junior and senior high school chemistry.

So the first one is obviously a disproportionation reaction, and the negative price of CL is already the lowest, so A to -1 is a price reduction, that is, A to B is going to increase the price, that is, -1C>A

The usual valence state of chlorine element: -1, 0, +1, +2, +3, +4, +5, +7, obviously the NaCl in one formula is -1, which is the lowest, that is, part of the Cl valence in A decreases to form NaCl, and the other part rises to form B, so B is higher than A, and the second equation is also a disproportionation reaction, that is, C is in the middle of A and B, so B>C > A.