Junior High School Chemistry! Hurry, hurry!

1. The addition of lime water can produce calcium carbonate precipitation through the reaction of calcium ions and carbonate, and no new impurities are introduced. Both option and d introduce chloride ions, while c all become sodium carbonate.

2. One mole of sulfuric acid needs to consume one mole of calcium hydroxide, which is 74g, and the same mole of sulfuric acid needs two moles of sodium hydroxide, which is 80g, and the same mass means that the calcium hydroxide should be excessive, and the solution is alkaline, and the pH is greater than 7The answer is greater than.

3、d。Dilute hydrochloric acid is added to create bubbles that make the lime water turbid. The gas that can make lime water turbid is carbon dioxide.

4、b。The removal of impurities requires that no new impurities are introduced, and carbon dioxide gas and sodium chloride are generated by hydrochloric acid reaction, and there will be no new impurities.

5、b。Nitrate produces a white precipitate, barium chloride does not react, and sodium carbonate has bubbles (gas escape). Three different phenomena can be distinguished. Nothing else.

6. The reaction is sodium sulfate and water, the solute mass decreases, and the water becomes a solvent. b does not react, so it does not change. c produces barium chloride, which has a higher molar mass than hydrochloric acid and an increase in solutes. d Zinc sulfate is generated, zinc has a higher molar mass than copper, and the solute mass increases.

7. The oxidation of silver nitrate is stronger than that of copper nitrate, and iron powder should react with silver nitrate first, and then react with copper nitrate completely. The addition of hydrochloric acid to the filtrate produces precipitation, indicating that there is silver nitrate in the filtrate, and copper nitrate does not participate in the reaction. So the precipitated metal is silver.

8. Silver chloride is insoluble in water. b No response. c Calcium carbonate is insoluble in water.

9. Calcium sulfate is slightly soluble, and barium hydroxide is insoluble. d. Iron hydroxide and barium sulfate are insoluble.

10、ac。Nitrates are soluble and cannot be removed in a one-step reaction. (I can't remember whether alkali melt can be remembered.) B plus hydrochloric acid i.e. d plus carbonate.

11、a。Because the amount of hydrochloric acid used is the same, the final amount of MgCl2 produced is the same, i.e., the solute mass is the same. A reaction produces hydrogen gas to escape and the mass of the solution decreases, while everything else has water production and the concentration decreases.

So a has the largest mass fraction of the solution.

12、b。Acid neutralizes the alkali and rinses with water. Insoluble bases are likewise soluble in acids.

B > B B No answer to question 6 B CD BC AC A B

D cannot be selected for the third question, and this will also occur with HCO3.

1) The first is to produce white precipitate BaCl2+H2SO4---BaSO4 +2HCl, and the second is BaSO4+2HNO3=H2SO4+BA(NO3)2

According to the solubility table of common acids, alkalis, and salts, Ba(NO3)2 is easily soluble in water, so there is no significant change.

2) Produce white precipitate BaCl2 + CuSO4 --- BaSO4 + CuCl2 The second is BaSO4 + 2Hno3 = H2SO4 + BA(NO3)2 or CuCl2 + HNO3 = Cu(NO3)2 + 2HCl, according to the solubility table of common acids, alkalis, and salts, Ba(NO3)2

Cu(NO3)2 is easily soluble in water, so there is no significant change.

1. Generate white precipitate; The precipitate insoluble equation is: BaCl2 + H2SO4 = BaSO4 + 2HCl

2. Generate a white precipitate, and the solution is blue; The pellet is insoluble, and the solution is blue; The equation is: BACL2 + CUSO4--- BASO4 + CUCL2

BaSO4, and AGCL are both acid-insoluble substances Thank you Good luck with your progress

Since it's a junior high school problem, it doesn't look like a competition question, so don't make it so complicated, hydrochloric acid and sulfuric acid, acids are the same as each other, acids can react with alkali to form salt and water, acid can react with alkaline oxides to form salt and water.

Acids can react with salts.

Acid energy and reactivity precede metal reactions in hydrogen.

The acid reacts with the indicator, and the litmus turns red.

As for the volatility of concentrated hydrochloric acid, the water absorption of concentrated sulfuric acid, and carbonized organic compounds, this junior high school should not be called writing equations.

As for calcium hydroxide and sodium hydroxide, let's talk about commonalities first.

Alkaline energy reacts with calcium hydroxide, sodium and hydrochloric acid.

Alkaline energy reacts with acidic oxides Sodium hydroxide Calcium and carbon dioxide Alkaline energy reacts with partial salts Copper chloride and sodium hydroxide Calcium.

The alkaline energy reacts with the indicator, the litmus turns blue, and the phenolphthalein turns red.

As for the deliquescent of sodium hydroxide, metamorphism is the reaction of calcium hydroxide with carbon dioxide, which is slightly soluble and neutralizes soil acidity.

2 Chemical properties of salts.

It can react with acids, find acids potassium carbonate and sulfuric acid.

It can react with alkali and find an alkali copper sulfate and sodium hydroxide.

It can react with metals, iron and copper sulfate.

It can react with salt, find a salt sodium chloride and silver nitrate.

Oxides can react with bases.

It can react with acids.

That's all you need to learn in junior high school.

Hydrochloric acid is a strong acid, with acid generality: it can make litmus and methyl orange red, can have a displacement reaction with metals with specific hydrogen activity, can neutralize with metal oxide (alkaline oxide) bases, and can metabolize with some salts.

2al+6hcl=alcl3+3h2↑

fe+2hcl=fecl2+h2↑

fe2o3+6hcl=2fecl3+3h2o

fe(oh)3+3hcl=fecl3+3h2o

fes+2hcl=fecl2+h2s↑

baco3+2hcl=bacl2+co2↑+h2o

agno3+hcl=agcl↓+hno3

Chloride ions in hydrochloric acid are weakly reducing and can be oxidized to chlorine by strong oxidants (such as KMno4, MNO2).

2kmno4+16hcl=2kcl+2mncl2↑+5cl2↑+8h2o

mno2+4hcl=mncl2+cl2↑+2h2o

Sulfuric acid is the same as hydrochloric acid.

Colorless and transparent sodium alkali liquid, is one of the strong alkalis, easy to dissolve in water, can react with many organic and inorganic compounds, is very corrosive, can burn the human body, etc.

Sodium hydroxide completely ionizes sodium ions and hydroxide ions in water and can be neutralized with any protonic acid. Take hydrochloric acid, for example:

naoh + hcl → nacl + h2o

Sodium hydroxide is also a good catalyst for many organic reactions. The most typical of these is the hydrolysis reaction of esters:

rcoor' + naoh → rcoona + r'oh

The reaction was carried out completely and quickly. That's why sodium hydroxide burns**.

Sodium hydroxide is one of the important raw materials for making soap. Add sodium hydroxide solution to oil, and the appropriate ratio will react and mix, becoming a solid soap. This reaction also uses the principle of hydrolysis, and this type of ester hydrolysis catalyzed by NaOH is called saponification reaction.

Uses Sodium hydroxide is widely used in various production processes. In chemical production, sodium hydroxide provides an alkaline environment or acts as a catalyst. The dilute solution of NAOH can be used as a washing liquid at home.

In food production, sodium hydroxide is sometimes used to process foods. Sodium hydroxide is even a necessary seasoning for a famous dish. Note that the use of sodium hydroxide at this time is strictly controlled; Some unscrupulous traders will use excessive sodium hydroxide to make food more "beautiful", but such food can cause disease.

Industrial Method. Sodium hydroxide is a by-product of the chlorine production process in industry. Electrolysis of saturated salt water until all the chlorine elements are converted into chlorine gas and escaped, leaving only sodium hydroxide as a solute in the solution. The reaction equation is:

2nacl + h2o → 2naoh + cl2 + h2

I don't know about the second question. Excuse me.

Metal oxides: can react with acids to form corresponding salts and water. Copper oxide + sulfuric acid = copper sulfate + water ** active metal oxide can directly react with water to form the corresponding alkali.

Calcium oxide + water = calcium hydroxide amphoteric oxide (alumina): alumina + hydrochloric acid = aluminum chloride + water; Alumina + sodium hydroxide = sodium metaaluminate + water.

Non-metallic oxides: reaction with alkali: carbon dioxide (small amount) + sodium hydroxide = sodium carbonate + water carbon dioxide (excess) + sodium hydroxide = sodium bicarbonate + water.

Reactive non-metallic oxides react with water to form acids in their valence states (with the exception of nitric acid). Sulfur trioxide + water = sulfuric acid.

The reactions of salts are mainly metathesis, redox and hydrolysis.

Metathesis requires a decrease in the concentration of ions in the solution after the reaction

Strong acid to weak acid: hydrochloric acid + sodium acetate = acetic acid (weak acid) + sodium chloride to generate precipitation: sodium sulfate + barium chloride = barium sulfate (precipitation) + sodium chloride to generate gas: hydrochloric acid + sodium carbonate = carbon dioxide + water + sodium chloride redox:

Sodium sulfide + sodium sulfite = sulfur + sodium hydroxide.

Hydrolysis reaction: ferric chloride = (reversible) iron hydroxide + hydrochloric acid.

Sodium acetate = (reversible) acetic acid + sodium hydroxide.

1. The first is not to touch the medicine with your hands, the second is not to bring Liang to smell the smell of the medicine closely, and the third is not to taste the taste of the medicine.

2. The oxygen in the flame core is insufficient, and the alcohol is not completely burned, so the temperature is low.

3. Turn off the alcohol lamp.

4. Observation and recording.

5. Slowly add items.

6. Experimental phenomena and experimental endpoints are recorded.

7. An element is a general term for atoms of the same class with the same number of protons (nuclear charges).

8. Physical change refers to the change of material form and color, and chemical change refers to the change of material structure. Therefore, there is not necessarily a chemical change in the physical change, but there must be a physical change in the chemical change.

1.Don't smell the medicine, don't touch the medicine with your hands, don't taste the medicine.

2. The alcohol is too closed and less carrying.

3. Extinguish the sedan chair and hold the alcohol lamp of Piling.

4. Observation Estimate.

In the experiment, if there is not enough alcohol in the burning alcohol lamp, the alcohol is added by first (extinguishing) and then adding alcohol to the alcohol lamp.

An important way to learn chemistry is experimentation, through experiments and careful (observation), accurate (calculation) and analysis and discussion of experimental phenomena, the principles of chemistry can be verified.

When weighing solid powders with a balance, the concept of how elements should be understood when the masses are close (using free codes) is generalized.

Physical change does not necessarily contain chemical change, but chemical change must contain physical change, how do you understand this sentence? It should be that there must be no chemical change in the change of Sun Zen in the dust, and if there is a chemical change, it is not a physical change, and there must be a physical change in the chemical change, because its state has changed, that is, the change of gas, liquid and solidity!

The relative molecular mass of sulfur dioxide is 64, and the relative molecular mass of sulfur trioxide is 80, and the oxygen mass ratio of the two is 2:3

The mass ratio of sulfur dioxide and sulfur trioxide with an oxygen mass ratio of 2:1 is to find the ratio of the number of o.

That is, 02:02=2:1--SO2:SO3=3:1, that is, 3*64:80=12:5

Solution: Knowing from 2:1.

3so2——so3

x 3*64/80）x

So they have a mass ratio of 12:5

Solution: Let the mass of sulfur dioxide be x and the mass of sulfur trioxide be y, then the mass of oxygen in sulfur dioxide.

Mass of oxygen in sulfur trioxide =

The ratio of the two is equal to 2:1

Find x y=12:5