All the scores of the chemistry questions in the third year of junior high school will be presented

1,2,3 are all correct, the answer to the fourth question is: C device: generate gas, the air pressure in the Erlenmeyer flask increases, the solution of the separating funnel will not flow down, and even bubbles will flow back, and the rubber stopper may pop out if it is dangerous.

Multi-purpose U-tube: generate gas, the air pressure on the right side increases, the liquid is pressed into the left, the liquid-solid is separated, and the automatic reaction stops, which is very scientific.

1) The names of A and B in Figure (I) are rubber head dropper and test tube respectively.

2) The advantage of using the "micro" instrument in Figure ( ) to do experiments is that only a very small amount of solids and a small amount of liquid (or only 1 2 droplets) is used for experiments

3) The role of device c in figure (i) is equivalent to that of device d in figure (ii), and their common advantage in experimental operation is to control the reaction rate by controlling the droplet acceleration of the liquid.

4) Rubber stopper flushed out (or Erlenmeyer flask**, 2 points) Liquid and solid are separated, and the reaction is stopped (2 points.

Hope it works.

C device: gas is generated, the air pressure in the Erlenmeyer flask increases, and the rubber stopper may pop out.

Multi-purpose U-tube: gas is generated, the air pressure on the right side increases, the liquid is pressed into the left, the liquid-solid is separated, and the reaction is stopped.

Otherwise correct.

1) Separate funnel Erlenmeyer flask concentrated sulfuric acid a

3) d The amount of liquid added dropwise.

4) In C, the rubber plug may pop out because the gas pressure is too large, and the experimental danger occurs.

The U-shaped tube presses the liquid upwards due to the gas pressure generated, so that the liquid is separated from the solid, and the reaction is stopped.

Sodium thiosulfate is selected because the oxygen in it is replaced by sulfur.

Calcium polysulfide, calcium sulfide is CAS, Ca is only combined with one S, now Ca is combined with multiple S, is calcium polysulfide.

Barium peroxide, originally barium oxide is BAO, and now BA is combined with peroxide O2, so it is barium peroxide.

In the title, the O in K2CO3 is replaced by S and is formed, and K2CS3 is therefore potassium trithiocarbonate. So choose A.

Choose a for this question, because the chemical formula is read from back to front, and K2CS3 is exactly potassium trithiocarbonate.

Choose a because S and O are of the same family, so they can be substituted. This compound may be similar in nature to potassium carbonate.

Elect A, its main structure is the front part.

12 grams of magnesium reacts with a sufficient amount of hydrochloric acid to produce 1 gram of hydrogen.

30 grams of magnesium reacts with a sufficient amount of hydrochloric acid to produce hydrogen:

30 1 12 grams.

65 grams of zinc reacts with a sufficient amount of hydrochloric acid to produce 2 grams of hydrogen.

30 grams of zinc reacts with a sufficient amount of hydrochloric acid to produce hydrogen:

65 2 30 g.

28 grams of iron reacts with a sufficient amount of hydrochloric acid to produce 1 gram of hydrogen.

30 grams of iron reacts with a sufficient amount of hydrochloric acid to produce hydrogen:

30 1 28 grams.

If 30 grams of hydrogen are produced each after the reaction, the masses of these three metals are required to be:

Magnesium: 12 30 360 grams.

Zinc: 65 30 2 975 grams.

Iron: 28 30 840 grams.

Zinc, magnesium, and iron are 30 grams each, and the amounts of the three substances are 30 65 mo, 30 24 mo, and 30 56 mo, respectively.

Then the quantities of substances that produce hydrogen are: mo, mo, and mo, and the masses of hydrogen produced are grams, grams, and grams, respectively.

If the reaction takes 30 grams to form H2 and the amount of substances to produce hydrogen is 15 mo, then the amount of substances that require these three metals is also 15 mo, and the mass of zinc is 975 grams, the mass of magnesium is 360 grams, and the mass of iron is 840 grams.

Let the mass of zinc be x

zn+h2so4=znso4+h2↑

65 2x solution gives x=

Cu% = A: The mass fraction of copper in the sample is 35%.

You calculate the amount of zinc participating in the reaction, five grams minus the weight of zinc, and forget all about the valency and everything, and you won't solve it.