There are a few problems with chemistry in junior high school

1, b2, carbon, because the candle burns to pick up the old carbon element, gathered in the cup low, the principle of charcoal burning.

3. Copper smelting, gold smelting, and manufacturing alum.

4. First, dip it in a little light, if there is a yellow flame, it is salt water; Second, add silver nitrate solution, there is a precipitate, it is saline.

5. The gas after combustion is collected and passed into the calcium hydroxide solution, and there is a precipitate, which proves that there is CO2; Dry copper sulphate is introduced and turns blue, and there is water.

Liquefied gas is a hydrocarbon, just like gasoline, but the molecular mass should be small.

The black is carbon black. 4.Sampling, heating.

It is to evaporate the two liquids, and the one with white crystals is salt water, and the other is distilled water. 5.

Liquefied gas is methane. The generation of carbon dioxide can be tested with lime water. The water should be tested with a dry glass sheet.

1. B because the smaller the graduated cylinder, the smaller the error.

2. The black carbon is burned after the product, and there are carbon components in the candle, of course, after burning. The principle behind is the same.

3. Papermaking, gunpowder, 4. The same volume scale mass, 5. First ignite the Sana slide and then put it on the top to see that there are water droplets, which means that there is water, and then inject the burned gas into the beaker that lights the candle, which will make the candle extinguish, indicating that there is carbon dioxide.

I've worked so hard, give it points.

, the more precise the better.

2.It's carbon. Candles do not burn completely, resulting in carbon loss.

The face black is also carbon, and the principle should be the same, it is the adsorption of carbon!

3.Gunpowder, metallurgy, alchemy.

4.Silver nitrate was added to the two liquids respectively, and the white precipitate was salt water, and the white precipitate was silver chloride.

5.The main component of liquefied gas is methane, take liquefied gas and burn, cover a cold and dry beaker above the flame, there will be water droplets, proving that there is water generation, and the gas produced by combustion is like clear lime water, lime water becomes turbid, proving that carbon dioxide is produced.

The closer the better).

2.Is it carbon due to the lack of oxygen that causes the candle to burn inadequately, producing small particles of carbon that aggregate at the bottom of the cup.

The principle is pretty much the same.

3.Alchemy, gunpowder, printing.

4.Evaporate a small amount of the solution with a silver nitrate solution (sodium ions react with chloride ions to form silver chloride precipitates) and observe for white particles.

Put an egg (hehe, it seems to be a bit mysterious).

5 The main components are propane, propylene, butane, butylene, and a small amount of pentane, pentene and trace sulfur compound impurities.

Verified carbon dioxide with clarified lime water Verification water with anhydrous copper sulfate (from colorless to blue in water).