Urgent! A few chemistry questions in junior high school, and standard answers, just write down the i

Sodium hydroxide is first deliquescent in the air, and then absorbs carbon dioxide, if there is 40 grams of sodium hydroxide, it will be 53 grams after complete deterioration

2NaOH+CO2====Na2CO3+H2O dilute hydrochloric acid does not react with copper, and the reduced test tube will be stained with copper element.

The other three are chemical changes NaOH+CO2====Na2CO3+H2O 3, CAO+H2O====Ca(OH Fe+3O2+6H2O====4Fe(OH)3), and the second is a physical change (concentrated sulfuric acid water absorption=dilution).

4. Formic acid (formic acid) and copper do not react.

5. It may be neutral.

The samples were all iron to produce hydrogen;

The samples were all zinc to produce hydrogen;

The samples were all made of aluminium to produce hydrogen.

The samples were all magnesium to produce hydrogen.

The samples were all copper to produce 0g of hydrogen

Because hydrogen is generated, impurities must produce less hydrogen than.

Either iron + zinc + copper, or iron + copper.

H2SO4+CaCO3====CaSO4+H20+CO2 Na2CO3+Ca(OH)2====2NaOH+CaCO3 alkali solution and copper sulfate will form copper hydroxide precipitate.

Let the concentrated sulfuric acid density be 1, 20%, and the sulfuric acid density is 2. (There is no density in the question) 500ml of 20% sulfuric acid mass = 500 2

It contains 500 2 20% sulfuric acid

Requires 98% sulfuric acid mass 500 2 20% 98% requires 98% sulfuric acid volume (500 2 20% 98%) 1 Requires water 500-(500 2 20% 98%) 11)CaCO3+2HCl====CaCl2+H20+CO2 20g xg

x=2）caco3+2hcl====cacl2+h20+co2↑__20g___yg

y=quality of water:

Quality of hydrochloric acid:

Mass fraction of solute in the original hydrochloric acid solution.

It's finally over!

1.Table salt does not deteriorate even if it absorbs water. Sodium hydroxide will deliquescent, that is, it will absorb water and deteriorate (if you don't understand deliquescent, check it). Concentrated sulfuric acid absorbs water, but it does not deteriorate, but only becomes dilute sulfuric acid. Concentrated hydrochloric acid volatilizes and the mass decreases.

2. The key is to see whether the chemicals in the option are soluble in dilute hydrochloric acid. Lime can, iron can, copper can't, ferric oxide can.

Option 3 134 is a chemical reaction and 2 is a physical reaction, which is the same as in question 1. (If you don't understand why chemistry is, then you must start all over again, and you don't have to waste time on problems).

4 Although you are not familiar with formic acid, but when it is an acid it is fine. Limestone can of course react with acid, aluminum can also replace hydrogen, there is iron in the steel bar, only copper cannot. (Be familiar with the table of substitution order).

5. Add phenolphthalein, if it is neutral, it will not change color.

6 This question is the application of the cross method, ask the teacher, I can't say it.

7H2SO4 + CACO3 = CASO4 (slightly soluble) + CO2 (gas) + H2O

8. Calcium carbonate and sodium hydroxide are generated.

Don't talk about the big questions, if you understand the basics, the big questions will have to be pulled.

Learn hard...

1.The answer is sodium hydroxide.

Because it deliquescent when placed in the air, and it reacts with carbon dioxide in the air to form sodium carbonate, the mass increases and deteriorates.

2.The answer is that after the reduction of copper oxide by hydrogen, the red solid residue attached to the test tube with red solid residue is copper, and the metallic copper will not react with dilute hydrochloric acid, so it cannot be disposed of cleanly.

3. The answer is that the quality of concentrated sulfuric acid placed in long-term exposure increases.

Because the other three all undergo chemical reactions and produce chemical changes, and the increase in the quality of concentrated sulfuric acid placed in long-term open is because the concentrated sulfuric acid placed in long-term open place has water absorption and absorbs moisture in the air, which is a physical change, so it is different from the other three.

4.The answer is copper products.

Because copper does not react with formic acid.

5.Answer: Drop into the phenolphthalein solution, the solution remains colorless, then the solution is acidic, because phenolphthalein can only make the alkaline solution red, but not acidic and neutral solution red, so the phenolphthalein test solution does not turn red, it may be acidic, or it may be neutral, so the answer is wrong.

I'm not too good at answering questions, so I'm sorry I can't help.

Meaning of "2" in 2NH3 (angular number 3) 2 NH3 molecules are represented by chemical symbols 3 hydroxide ions 3(OH-) The valency of the underlined element.

kclo3 "cl" +5

kmno4 "mn" +7

k2mno4 "mn" +6

hclo "cl" +1

nh4no3 "n" "n"Anterior -3 posterior +5cl2o7"cl" +7

cah2 "h2" -1

nh3"n" -3

h2o2"o2"One o is -1 valence and two o's are -2

Evaporation is carried out and the alcohol will evaporate away, while the brine will leave sodium chloride crystals and the sample will ignite the alcohol flammable and the brine cannot be burned.

aOxygen can support combustion.

What color, density are all physical properties.

1 Physical Method: Smell the Smell...

Chemical method: + silver nitrate, salt water with precipitation, + sodium, ethanol with hydrogen release.

2 A flammability is a chemical property.

1. Physical method: smell the smell: the one with a faint fragrance is alcohol, and the other bottle is salt water.

Chemical method: Add a few drops of silver nitrate solution, there is a white precipitate is a sodium chloride solution, and another bottle is industrial alcohol.

2. Choose A, liquid oxygen is blue, which describes the color and physical properties.

1 After the fourth addition of dilute hydrochloric acid, no gas is generated, leaving a solid mass that is the mass of impurities, so the impurities are.

2 The ore consists of two parts: calcium carbonate and impurities, so the mass of calcium carbonate is, and the mass fraction can be found next.

3 The reaction is not completely over until the third reaction, so the mass reduced by the first three reactions is the same each time. m=

4. The mass fraction of 80% limestone is required to be XCACO3, high temperature CAO+CO2

100 (calculate the relative molecular weight of CAO) 80% x 280kg

List the proportional formula, and find that x is the limestone mass).

Solution: (1) The mass of CAC2O4 generated by 10ml of blood conversion is X.

cac2o4+h2so4=caso4+h2c2o4x

Punch this round 128 x=90

x=2).

Mass of ca per liter of blood sample = (1000 10).

88mg＜100mg＜108mg

The blood sample has normal calcium levels

Answer: The mass of CAC2O4 generated by the transformation of 10ml of blood is 100mg per liter of the blood sample, and the calcium content of the blood sample is normal

This is the question of the third year of junior high school. Nima, for Mao, we learned it in the second year of junior high school... Chemical poisoning is quite deep.

Except for 5 cotton, 6 flour, and 7 edible oil, the others are strictly prohibited, so the answer is d

1 gunpowder 2 paint 4 detonators.

8 Alcohol Answer: D