Chemistry questions, laboratory tests, who knows?

Steps: 1) Calculation: Calculate the mass of the solid solute or the volume of the liquid concentrated solution required for the preparation.

The volume of concentrated phosphoric acid is required

2) Weighing: Weigh the solid mass with a tray balance or measure the volume of the liquid with a graduated cylinder (a pipette should be used, but a graduated cylinder is generally used in secondary school). Measure milliliters of concentrated phosphoric acid.

3) Dissolving: dilute concentrated phosphoric acid in a beaker and return to room temperature (if it cannot be completely dissolved, it can be heated appropriately). Check the volumetric flask for water leaks.

4) Transfer: Carefully transfer the cooled solution in the beaker along the glass rod into a certain volume of volumetric flask (the lower end of the glass rod should be below the scale mark of the volumetric flask).

5) Washing: Wash the beaker and glass rod 2 3 times with distilled water, and transfer the washing solution to the container, shake, so that the solution is mixed evenly.

6) Constant volume: When adding water to the 500ml volumetric flask to 1cm 2cm below the scale line, use the rubber head dropper to add water instead, so that the concave surface of the solution is exactly tangent to the scale mark.

7) Shake well: Cover the cork, press the cork with your index finger, hold the bottom of the bottle with the fingers of the other hand, and turn it upside down repeatedly to mix the solution evenly.

Finally, the prepared solution is poured into the reagent bottle and labeled.

1.Volume of concentrated phosphoric acid

2.Use a graduated cylinder to measure milliliters of concentrated phosphoric acid.

3.Dilute concentrated phosphoric acid in a beaker and return to room temperature.

4.Carefully transfer the cooled solution in the beaker along the glass rod.

5.Wash the beaker and glass rod in a volumetric flask of a certain volume with distilled water, and transfer the washing solution to a container and shake to make the solution mix evenly.

6.When adding water to the 500ml volumetric flask to 1cm 2cm below the scale mark, use the rubber tip dropper to add water instead, so that the concave surface of the solution is exactly tangent to the scale mark.

7.Cover the cork, press the cork with your index finger and hold the bottom of the bottle with the fingers of your other hand, and turn it upside down repeatedly to mix the solution evenly.

8.Finally, the prepared solution is poured into the reagent bottle and labeled.

Summary. Problem solving process:

The mass of magnesium and zinc is equal, so according to the law of conservation of mass, both of these elements flow into the salt solution, so the mass of magnesium and zinc is equal, but from the chemical equation, the number of MgCl2 particles is much more than that of ZnCl2, so the mass of chlorine is increased, so the mass of MgCl2 is more than that of ZnCl2, and magnesium reacts more easily with activity, that is, the reaction is faster, so the salt mass is produced faster.

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Problem solving process: The mass of magnesium and zinc is equal, so according to the law of mass constancy, these two elements flow to Tongfan in the salt solution, so the mass of magnesium and zinc elements is equal, but from the chemical equation, the number of MgCl2 particles is much more than that of ZnCl2, so the mass of chlorine is increased, so the mass of MgCl2 is more than that of ZnCl2.

Dear, please take a look.

The abscissa of the title is dilute hydrochloric acid.

I see, dear. B error is that mg is more active than zn on the image, so mg reacts faster.

Dear, do you understand that?

mg comes first to equilibrium, not zn comes first to equilibrium.

The image should look like this:

No, the abscissa of this image is dilute hydrochloric acid, when there is a small amount of dilute hydrochloric acid, and the salt of zinc chloride is more than magnesium chloride, dilute hydrochloric acid is sufficient, and magnesium emits more hydrogen, so magnesium chloride is more than zinc chloride, the abscissa of this question is dilute hydrochloric acid, there is no balance between fast and slow, and I can also send a message.

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Dear, do you understand that even if Qing does this dilute hydrochloric acid in small amounts, the hydrogen released by the two is the same, and the amount of dilute hydrochloric acid is more hydrogen per release, so for example, because when there is a small amount, for example, there are only two HCl, because the heart and beauty are excessive, there are two Yu Xun HCl, then one hydrogen will be generated.

I know, the abscissa is dilute hydrochloric acid, at the beginning the amount of dilute hydrochloric acid is small, and the amount of hydrogen is generated, but the salt is not the same, and magnesium chloride is definitely less than zinc chloride.

When there are many dilute hydrochloride oranges, equal quality metals, magnesium releases more hydrogen, consumes more dilute hydrochloric acid, magnesium and zinc and other qualities, but magnesium chloride has more chlorine elements, so the quality of magnesium chloride is greater than that of zinc chloride.

The relative molecular mass of magnesium is greater than the relative molecular mass of the conscious and therefore the last green flower is more intelligent.

Mg and Zn react with excess hydrochloric acid at the same mass, and the mass of magnesium chloride produced is larger.

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1. The laboratory uses potassium chlorate and manganese dioxide to produce oxygen, and the mouth of the test tube into a solid drug should be slightly inclined downward, and the iron clamp should be clamped about one-third from the mouth of the test tube.

2 The existing A g KCLO3 is mixed with B g Mno2 and heated, heated until the mass is no longer reduced, and the remaining solid C g is obtained, then the mass of oxygen generated by the reaction is ( A + B-C ) grams, and potassium chloride (C-B) grams will be generated at the same time.

3 Methanol is a toxic and flammable liquid with the smell of alcohol. The incomplete combustion of methanol in oxygen can cause the following reactions.

8CH3OH+NO2 ignites MCO2+2CO+16H2OIf the reaction produces grams of water, calculate:

The amount of methanol participating in the reaction is (10)mol, and the amount of substances that produce CO is (140)mol

4 The process of chemical reaction between hydrogen and oxygen is described in the following diagram as a macroscopic description, and what information can be obtained in addition to the meaning of the chemical equation itself (write two items).

1) Water is composed of hydrogen and oxygen.

2) A water molecule is composed of 2 hydrogen atoms and 1 oxygen atom.

1 Homogeneous drug department.

2 a+b-c

34Water is composed of two elements, hydrogen and oxygen, and the ratio of the number of molecules of hydrogen and oxygen in the reactants is 2:1

1.Homogeneous drug site.

Add b minus c c minus b

4.In chemical changes, molecules can be redivided, while atoms can no longer be divided Molecules are made up of atoms.

1.I don't know what it is than the inverted type?

2.All the above equations are 2kclo3=(heating)2kcl+3o2(gas).

KCl + AGNO3 = AGCL (precipitation) + KNO3 should be a complete reflection so it is obtained according to the grams of AGCL precipitation.

That is, kcl is because all cl elements are in kclo3 and kcl, and because kclo3 is decomposed, no cl elements are consumed.

So the mass of Cl is the mass of the chlorine element in the original mixture.

3.From the second question, it can be seen that the amount of KCl is (39+ The mass of oxygen is the mass of the gas produced by heating the solid mixture.

It's too much to calculate, so it's supposed to be chemistry in the second year of high school.

(1) C7H10O5,2) is the addition reaction of Br2 and C=C double bonds, the equation is: C7H10O5+Br2 - >C7H10O5Br2, and the two Br atoms are added to the two C atoms of C=C in the middle of the period.

3) C7H10O5 + NaOH = C7H9O5Na + H2O, only the ionized H+ in -COOH will neutralize with NaOH, and the others are alcohol hydroxyl groups and do not react.

4), because 1 C7H10O5 contains 1 -Cooh, which reacts with 1 NaHCO3 to generate 1 CO2 molecule, the chemical equation is: C7H10O5 + NaHCO3 - > C7H9O5Na + CO2 (gas) + H2O, and the relative molecular mass of C7H10O5 is 174, so the amount of its substance is, so the final generated CO2 is also, converted into volume.

c7h10o5

Bromine adds to double bonds.

Ordinary acid-base neutralization reaction.

First calculate the relative molecular mass of a 174, the reaction can be generated, I don't remember how much.

Select the amount of matter of the atom contained in H2O2 as.

The amount of matter of the atom in a is .

The amount of matter of the atom in b is.

The amount of matter of the atom in c is.

The amount of matter of the atom in d is.

If there is no accident, it is B. Just multiply the number of corners under each element by the moles in front of it. Add it up again.

Hydrogen peroxide. Only phosphoric acid is also.

It's been a long time since I've done chemistry. I forgot about it, right? ll refer to it yourself.

Choose to have atoms 2+2=4 and have atoms then b again.