Chemistry questions for answers, ask for help from well wishers Will write a few questions Write a f

5 For bread grows hairy, and the vegetables become sour, and the apples have rotten pieces.

1. Chemical changes.

2. Physical changes.

3. Chemical changes.

4. Physical changes.

5. Chemical changes.

6. Physical changes.

7. Physical changes.

8. Physical changes.

Physical changes: 2, 4, 6, 7, 8, the rest are chemical changes.

The main difference between a physical change and a chemical change is whether or not a new substance is produced.

Physical properties: 2, 3, 6, 7, the rest are chemical.

Physical Change: No change in the formation of other matter, only a change in the shape and state of the matter.

Chemical change: There is a change in the production of new substances, also known as chemical reactions.

With these two items, the above questions can be judged.

Iron rusts chemical changes and new substances are generated.

Paraffin wax melts physical changes and morphological changes.

Paper burns chemical changes and new substances are generated.

Porcelain bowl broken physical change morphological change.

Copper produces patina in moist air, chemical changes, and new substances are formed.

Wet clothes are dried by physical changes evaporating.

After the snow, the weather is sunny and warm, and the snow melts Physical changes and morphological changes.

In the cold winter, when you puff into the window glass, there will be a layer of water mist Physical changes Morphological changes.

2.What is the main difference between physical change and chemical change? How can you tell if a substance has undergone a chemical change? Illustrate.

The main difference: whether new substances are formed. If a substance undergoes a chemical change, the original substance is destroyed to form a new substance. Such as gasoline burning.

3.Which of the following descriptions of the properties of matter refer to physical properties and which refer to chemical properties? Why?

Alcohol can burn chemical properties.

Alcohol is volatile due to its physical properties.

Water becomes water vapor with physical properties.

Using grain as raw material can make wine chemical properties.

Carbon dioxide can be clarified by the chemical properties of lime water that becomes turbid.

Air is a gas with no color, no smell and physical properties.

The density of copper is g cm cube and the melting point is 1083 physical properties.

Limestone [or marble] produces carbon dioxide and water chemistry when it encounters hydrochloric acid.

Because the ability to generate new substances is chemical.

4.Observe substances around you, such as water, salt, sucrose, copper, etc., and describe their properties and uses.

Water, Physical Properties: Flowing liquid, non-flammable, volatile, boiling point 100 degrees Celsius Freezing point: 0 degrees Celsius Usage:

Extinguish the fire and control the temperature. Chemical properties: Reacts with active metals and is a polar substance.

Function: such as reacting with carbon to form water gas.

Table salt, the main ingredient sodium chloride, its aqueous solution can conduct electricity, use: pickled food, because its aqueous solution has a large osmotic pressure.

Sucrose, a colorless solid, is an organic substance that can be used to flavor food.

Copper, a metal element, is malleable and conductive, and is often used in the production of cables.

5.Life experience tells us that food has a certain shelf life, and spoiled food should never be eaten. What are the phenomena that can help us tell that food has gone bad, for example.

For example, the color of the food changes, mildew, and the phenomenon of the packaged food is enlarged, indicating that the food has deteriorated.

Such as steamed bread blackened and moldy.

By n(n+2) under the root number of = roots, the number of solitary electrons of the following complexes and other answers can be obtained.

1) [Fe(en)3]2+, n=5, the hybrid orbital type is sp, the space type is linear, it belongs to the outer orbit type, and belongs to the high spin.

2) [co(scn)4]2-, n=4, the hybrid orbital type is sp3, and the spatial configuration is regular tetrahedron, which belongs to the outer orbit type and belongs to high spin.

3) [mn(cn)6]4-, n=3, the hybrid orbital type is sp3d2 hybridization, and the spatial configuration is regular octahedron, which belongs to the outer orbit type and belongs to high spin.

4) [Fef6]3-, n=5, the hybrid orbital type is DSP3 hybridization, and the spatial configuration is trigonal double cone, which belongs to the outer orbit type and belongs to high spin.

5) [Ni(CN)4]2-, n=0, the hybrid orbital is DSP2 hybrid, and the spatial configuration is a planar body, which belongs to the inner orbital type and belongs to low spin.

6) [Ni(nH3)6]2+, n=3, the hybrid orbit is sp3d2 hybridized, and the space configuration is regular octahedron, which belongs to the outer orbit type and belongs to high spin.

The following formula is required:

g=-rtlnk

g=δh-tδs

First of all, since the δg of the reaction is known, the k= of this reaction at 298k can be calculated according to Equation 1. Because for this reaction, k=p(o2) p0, so p(o2) can be obtained as an atmospheric pressure, which is 12pa.

According to Equation 2, since δg, δh, and t are all known, δs = j mol can be solved. When the temperature change is not large, the change of reaction enthalpy and reaction entropy can be ignored, because when δg<=0, the silver oxide decomposes, so when δg=0, t=, that is, Celsius, can be solved.

Because the concentration of the original solution is 2000 μg ml, 5 ml contains solute: 10000 μg. Before and after dilution of the solution, the mass of the solute is unchanged, and the volume of the solvent becomes 100 times the original, so the concentration of the diluted solution is:

10000 (5*100) = 20 micrograms of ml.

Although your answer is wrong, in the problem of solution dilution, just remember one important point: the amount before and after solute dilution is constant. This is the most critical and the core of the problem about solution dilution.

The mass of the solute is constant, only the total volume of the solution is changed. 2000 5 (5 100) = 20 micrograms of milliliters. Your answer is questionable, thanks.

It should be diluted to 100ml, so that it can be calculated that it is 2000 5 100 = 100 micrograms.

Answers b, c, a, d

Analysis: There are 3 stable isomers of the molecular formula C3H6O: acetone, propionaldehyde, and propenol A can react with Schiff's reagent, indicating that A is propionaldehyde (Schiff's reagent can be used to identify aldehydes and ketones. After the action of aldehydes and Schiff's reagent, the solution is purplish-red, and usually, ketones do not react with Schiff's reagent).

Based on the conditions, B is inferred to be acetone.

A hydrogenation to produce C is 1-propanol (primary alcohol); b hydrogenation to produce d as 2-propanol (belonging to the secondary alcohol position, which is called primary, middle, uncle, and quarter.

The mass of manganese dioxide is always the same, and its mass fraction changes, indicating that the total amount of solid matter has changed.

The original content was, and later came to 30%.

Illustrates that the mass ratio of the original solid to the present solid is 60:53, a decrease of "7".

The mass of manganese dioxide is (60*

Potassium chlorate mass (original) is".

2kclo3===2kcl+3o2

then the original potassium chlorate is decomposed".

The decomposition rate is.

2kclo3===2kcl+3o2, the mass is reduced by 96, since manganese dioxide is a catalyst, the mass before and after the reaction remains unchanged, let the mass before the reaction be x, and the mass after the reaction is y, then there is, find x y=60 53, the mass is reduced by 7, according to the chemical equation, solve that in a mixture of 60 grams, potassium chlorate is decomposed, then its decomposition rate is.

The ratio of 44g mol volume is equal to the ratio of the quantity of the substance, the ratio of pressure is equal to the inverse ratio of the amount of the substance, and when the mass is the same, the ratio of the quantity of the substance is equal to the inverse ratio of the molar mass 16:4=x:11

a、cb、co2

c、cod、o2

e、cuof、fe2o2

The equation for variation: Fe2O3 + 3Co = High temperature = 2Fe + 3CO2

I have long forgotten the title of what era.

1.The gas is more efficient in fuel combustion, and the resources are more fully used. High calorific value of combustion.

2.Toxic, combustible and soluble in water.

Run in the direction of the headwind, covering your mouth and nose with a wet wipe.

1. High calorific value, no waste circular fiber residue.

2. H2S is toxic and flammable, and orange imitation is soluble in water. Move to the heights of Langchun and wear a gas mask or cover your mouth and nose with a wet towel.

1: It is more convenient to burn more fully and transport it back to the relatives.

2:1, flammable, gas, toxic, soluble in water (appearance).

2. Cover your mouth and nose with a wet towel to escape At this time, you should stay away from the possible fire source.