Urgency A science question in grade 9 and a few multiple choice questions in grade 9 science

First of all, from the fact that the precipitate can be completely dissolved and gas is generated, it can be inferred that the precipitate must be carbonate, which indicates that the original solid contains sodium carbonate.

Then it can react with sodium carbonate to form a precipitated substance of barium chloride. Because the precipitate is completely dissolved in dilute hydrochloric acid, sodium sulfate must not be present, otherwise the resulting barium sulfate cannot be dissolved in hydrochloric acid.

From the above, it is known that the white solid must have sodium carbonate, barium chloride; No sodium sulfate. As for sodium hydroxide, I still can't tell if it exists from the title, so choose A

Sampling is soluble in water, and white precipitate is produced This sentence can judge that the white items are not sodium hydroxide and sodium sulfate, sodium hydroxide is very soluble in aqueous solution and colorless, while sodium sulfate is insoluble in water!!

After filtration, hydrochloric acid is added dropwise to the white precipitate, and the precipitate is completely dissolved and gas is produced This sentence can determine that the white item is not barium chloride, because the reaction between barium chloride and hydrochloric acid does not produce gas!! So choose C!!

Sampling dissolved in water has a white precipitate produced", the precipitate may be barium sulfate, barium carbonate, barium hydroxide.

After filtration, hydrochloric acid is added dropwise to this white precipitate, and the precipitate is completely dissolved and gas is generated", excluding barium sulfate.

completely dissolved and gases produced". Then there must be barium carbonate, and barium hydroxide cannot be judged.

Therefore, there must be no sodium sulfate in the original white solid, sodium carbonate, barium chloride, and sodium hydroxide may be there.

Therefore, answer A is correct and BCD is wrong.

A (just checked, indeed A).

c. The environment that creates hypoxia is conducive to lactic acid fermentation.

c Renal tubules Question 2 Because acetic acid bacteria make vinegar. Kimchi requires lactic acid bacteria, and lactic acid bacteria fermentation requires an oxygen-free or oxygen-deficient environment, so water is poured into the kimchi jar to prevent air from entering.

Question 3 Inertia is only affected by mass and has nothing to do with velocity.

1. The right binding post of the voltmeter is connected to the right binding post of the small bulb.

2. Right. 3. r=u i=6v 1a=6 ohms.

4. The total power consumed by the circuit is the largest, according to the formula p=ui The power is the largest, and the voltage is unchanged, then the maximum current is required, that is, the current when the small bulb emits light normally i=1a The rheostat consumes power p=ui=(9V-6V) 1A=3W

The right end of the voltmeter is connected to the right end of the bulb; Right; The figure is not clear, find the current corresponding to 6V, and divide the two; 3V multiply the current found in (3) The claw machine is not forceful, and the diagram cannot be seen clearly. . .

There is no picture, I can only rely on my understanding.

1.Long pipes in and short pipes out.

2.Clarified lime water. ca（oh）2+co2===caco3↓+h2o3.Short tubes, long tubes, graduated cylinders.

4., I can't help without love. : Potassium chloride heating to produce oxygen: iron frame (with iron ring), alcohol lamp, test tube, catheter, if it is collected by air exhaust method, it is necessary to collect gas cylinders and glass sheets, if it is drainage law, it is a sink and gas collection cylinders and glass sheets.

Dilute hydrochloric acid and marble limestone for carbon dioxide: Erlenmeyer flasks, catheters, gas collection cylinders, glass sheets.

5.Volumetric flasks.

6.Solve the picture by yourself.

Big question. That's right, too.

8.Ditto. Put the burning wood on the mouth of the bottle, and if it is extinguished, it will be full.

10.Solid heating type. Move the tube first and then turn off the lights.

11.I don't have a picture, I write it myself.

12.Exhaust the air inside to prevent **.

13.Suppose the black solid is MnO2 and the colorless solution is H2O2

14.Collect the gas and put the wood with the spark into the bottle.

15.Bubbles are produced, and the black solid does not change less than the re-ignition of the wooden strip with sparks.

Catalysis) 2H2O+O2.

17.This gas is O2

It's over.,Write it yourself if you don't have a picture.。

1.Long in and short out.

2.Cleared lime water is introduced.

3.Short, graduated cylinder.

There's no picture in the back.。。。

If you don't give the old picture, you can't explain it in detail.

6*10 5 j (law of conservation of energy), less than (also converted to other energies, such as heat energy when turning).