Junior high school chemistry questions, urgent, high scores, additional points for good answers, com

Calcium hydroxide becomes sodium hydroxide: Ca(OH)2 + Na2CO3 == 2NaOH + CaCO3

Calcium carbonate becomes calcium hydroxide: CaCO3 + 2HCl == CaCl2 + H2O + CO2

CaCl2 + 2NaOH == 2NaCl + Ca(OH)2 (Ca(Oh)2 slightly soluble).

Magnesium sulfate becomes magnesium chloride: MgSO4 + BaCl2 == MgCl2 + BaSO4

Magnesium chloride becomes magnesium carbonate: MgCl2 + Na2CO3 == 2NaCl + MgCO3

Calcium carbonate becomes calcium hydroxide.

Calcium carbonate, pyrolysis CA plus water.

Magnesium sulfate becomes magnesium chloride.

Magnesium sulfate plus silver chloride.

Calcium carbonate is decomposed at high temperature to produce calcium oxide and carbon dioxide, and calcium oxide is added to water to produce calcium hydroxide.

Magnesium sulfate plus barium chloride produces barium sulfate precipitate and magnesium chloride.

Magnesium chloride plus sodium carbonate produces magnesium carbonate precipitate plus sodium chloride.

The first sodium hydroxide became sodium hydroxide? Is there a mistake?

1.The first one seems to be a mistake, and you can see again.

2.After high temperature, it becomes calcium oxide and carbon dioxide, which is then added to water.

3.Add sodium hydroxide to magnesium hydroxide, and then add magnesium hydroxide to hydrochloric acid.

4. It directly reacts with sodium carbonate to form magnesium carbonate and sodium sulfate.

Sodium hydroxide becomes sodium hydroxide? Make a mistake.

Calcium carbonate becomes calcium hydroxide First calcined calcium carbonate at high temperature to turn it into calcium oxide, and then add water to make calcium oxide react with water to form calcium hydroxide.

Magnesium sulfate becomes magnesium chloride and can be filtered with barium chloride.

Magnesium chloride becomes magnesium carbonate MgCl2 + Na2CO3 = MgCO3 +2NaCl

1. Add an appropriate amount of sodium carbonate.

2. Add excess hydrochloric acid first, and then add excess sodium hydroxide.

3. Add an appropriate amount of barium chloride.

4. Add excessive sodium carbonate.

Sodium hydroxide becomes sodium hydroxide, what is it?

1. No, the reason is very simple, explain: carbon dioxide and water vapor are generated after combustion, which volatilize into the air, and the mass is actually not reduced, of course, for candles, it must be reduced. Just like when you eat, if you eat one bite, you will lose one bite of food!

2. Magnesium is burned in the air to produce magnesium oxide, you can see according to the chemical formula, the magnesium element is not reduced, on the contrary, the oxygen element is increased, according to the mass conservation of the chemical reaction, the increased mass is the oxygen quality required for burning magnesium.

Paper is a mixture, the combustion is mainly the combustion of carbon, the result of combustion is the formation of carbon dioxide, the rest is those impurities, obviously, carbon dioxide is integrated into the air, the conservation of mass is known, and the mass is reduced.

If you know the chemical equation for the decomposition of potassium permanganate, you will know why the residue is less mass than the reactant, and the decomposition produces oxygen, water and potassium manganate. The rest you see is potassium manganate, and oxygen and buckets.

3. After the substance is heated in a vacuum and reacts, the total mass of the product must be equal to the total mass of the reactant.

After the fine iron wire is burned in oxygen, the mass of the product is greater than that of the fine iron wire, so this reaction does not obey the law of conservation of mass.

Obviously not, the iron oxide and ferric tetroxide generated, I don't want to talk about it below.

Brother, study hard, I've been in college for more than three years, and I think it's better to study in high school.

Since the products are formed by other gases, they volatilize, resulting in the conservation of mass, but it cannot be said that they do not obey the law of conservation of mass.

1.No, candles burn to produce carbon dioxide.

But carbon dioxide is not counted in the sum of the masses of the product, so that doesn't mean that the law of conservation of mass is not universal.

2.Paper is burned in the air and turns into ashes, and the mass of the ashes is smaller than that of paper.

3.The iron wire combines with oxygen in the air to form ferric tetroxide, so it is larger than the original iron wire.

1 Conservation of mass means that the mass of the substance remains unchanged before and after the reaction in the whole system, the candle burns and reacts with oxygen to form other substances, volatilizes into the air, and after the reaction, it is only called the candle, so the mass decreases, but does not conflict with the law of conservation of mass.

2 Magnesium strips are burned to produce magnesium oxide.

Paper burns to produce CO2

Decomposes to produce oxygen.

3 React in a closed system.

A Red iron oxide powder is reduced and gradually turns black (Fe2O3 + 3Co = heating = 2Fe + 3Co).

b. Clarified lime water gradually becomes turbid (CO2+Ca(OH)2===CaCO3+H2O).

c Excess CO is burned (2CO + O2 = ignition = 2CO2).

(1) A: The red substance becomes the black substance Fe2O3+3CO====2Fe+3CO2 (the condition is written as high temperature or heating).

B: The clarified lime water becomes turbid Ca(OH)2+CO2=CaCO3+H2O

C: Combustion of the vented gas 2CO+O2=2CO2 (conditional ignition).

The substance in the glass tube turns black, and the equation Fe2O3 + 3Co = 2Fe = 3CO2. The clarified lime water becomes muddy, and the equation CO2 + CA(HO)2 = CAC3 (precipitation) + H2O. Carbon monoxide combustion, equation 2CO+O2=2CO2.

There is no ab c on the diagram, so the order may not be right.

The red powder turns black.

Fe2O3+3Co high temperature = 2Fe+3CO2

CO2 + CA(OH)2 = CAC3 solid symbol + H2O emits a blue flame.

2CO+O2 ignition = 2CO2

Heating turns red, ferric oxide is heated to form iron, lime water becomes turbid.

1.We know from our studies that iron rusts when placed in the air, while copper will have the same phenomenon. The process of copper rusting is the reaction of copper with oxygen in the air and two other substances in the air to form a layer of patina [the chemical formula is Cu2(0H)2CO3] on its surface, please speculate that the other two substances in the air that react with it are water and carbon dioxide.

2.In the earth's crust, iron exists in the form of compounds due to its relatively reactive chemical properties; In ferroalloys, the iron element exists in elemental form, and the valency of the iron element is zero.

3.An ironmaking plant smelts pig iron from hematite containing impurities 20 (the main component is Fe2O3). Find the mass of pig iron containing 98 Fe from 4000kg of this ore (keep the L decimal place).

4000kg This ore contains a mass of 4000kg * (1-20%) = 3200kg

fe2o3+3co=3co2+2fe

3200kg x*98%

160/3200kg=112/x=

1. Water vapor and carbon dioxide.

2. Oxide and iron are easily oxidized by oxygen in the air in a humid environment; Elemental, zero price 3,

Analysis: Let the mass of pig iron be xkg. According to the conservation of iron, the column equation is as follows:

4000*(1-20%)*112/160)=x*98%x=

Note: 112 160 is the mass fraction of iron in Fe2O3.

1. CO2 and H2O

2. Compounds and iron elements are relatively active, reducible, elemental, and 0 valent.

1：co2 , h2o

2: The chemical properties of iron are more active in the form of compounds; elemental, 0

It is the iron content of Fe2O3.