Junior High School Chemistry Questions! Chemistry Ace! 15

2, the reaction of calcium oxide and water is a chemical reaction, not a metathesis reaction!

cao+ h2o =ca(oh)2

Ca(OH)2 + Na2CO3 = CaCO3 (precipitate) + 2NaOHCA(OH)2 + K2CO3 = CaCO3 (precipitate) +2koH

I'm a chemistry teacher, and we just did this question two days ago, and the answer is: two.

Problem solving process: CaO+H2O=Ca(OH)2 (chemical reaction) Ca(OH)2+Na2CO3=CaCO3 (precipitation)+2NaOH (metathesis reaction).

Ca(OH)2 + K2CO3 (the main component of plant ash) = CaCO3 (precipitation) + 2koH (metathesis reaction).

In summary, a total of 3 reactions occur in the whole process, two of which are metathesis reactions.

The answer should be 3...

Calcium oxide and water.

Potassium carbonate and calcium hydroxide.

Sodium hydroxide (from the reaction of water and sodium carbonate, you may be wrong now, but that's just the way it is) and calcium oxide.

(1) m=ρv=

2) 2kmno4 = k2mno4 + mno2 + o2 ↑2*158 197 87 32

x y zx=2*158*

y=197*

z=87*The potassium permanganate in the reactant is 80 grams, and only the grams are not completely reacted, and the residue is potassium permanganate.

Potassium manganate manganese dioxide.

(1) 1.Fill a balloon with carbon dioxide and the balloon will fall down 2Make a simple balance to the first: 1Looking at the chemical amount, the average amount of carbon dioxide is 44, while the average amount of air is 29

(1) m = density * volume =

2) The remaining solids are manganese dioxide and potassium manganate.

1. Measure the density, the density of salt water is larger, and the density of fresh water is 1 ton cubic meter.

2Put a piece of radish, fresh water: the radish absorbs water. Salt water: The radish loses water and becomes soft.

3. The alcohol lamp is heated to evaporate the water, and the salt analysis is salty water.

4Find a cotton thread and put it in water, then take it out to dry, and burn it with fire, if the cotton thread can be ignited, it is fresh water, otherwise it is salt water.

5. Add silver nitrate to see if there is any precipitation.

It is a copper-zinc alloy, in fact, there is no need to calculate, the reasons are as follows:

The first one has bubbles, indicating that it will not be a copper-silver alloy, because neither copper nor silver will react with dilute sulfuric acid;

After the second reaction, a colorless solution is obtained, indicating that it will not be a copper-iron alloy, because if it contains iron and reacts with Cu2+, the color of the solution should be light green;

Through the first one it is known that 10 grams of alloy contain grams of copper, and another alloy grams. Through the second part, it was seen that the weight of the metal decreased from 10 grams to grams after the reaction. The instructions can only be copper-zinc alloys.

2al-3cu2+ -3cu makes the metal mass heavier.

Copper-zinc alloy. First of all, the first part is a sufficient amount of sulfuric acid, so it reacts except for copper.

So ten grams of alloy, copper is grams.

So in the second experiment, because the gram solids are insoluble in sulfuric acid, they are all copper.

Copper is replaced with grams.

First of all, copper and silver can be excluded and will not react with sulfuric acid.

In the case of copper and iron, iron ions are colored. So it can't be.

Aluminum reacts with water first and cannot replace copper.

So from the data, and that's just the look.

It can only be copper-zinc alloy!

It should be a copper-iron alloy.

1.Copper and silver react with acid without phenomenon, so copper-silver alloys are excluded.

2.All that remains is iron reacting with copper sulphate to form ferric sulphate precipitates.

Well, I'm sorry, although I know how to solve it, but I forgot all about the mass constant.

Do it with the difference in the amount of travel Qi shooting method.

Before and after the reaction, the amount of solid mass decreases ==

H2 + Cuo == High temperature == Cu + H2O mm

80/m = 16/

m = so cuo quality is.

The CU mass is - =