A chemistry quiz question, ask a chemistry question.

First of all, one thing is clear, in the formula to determine the positive and negative reaction heat, value? Observed h, h

0 reaction endothermic description, h <0 description exothermic reaction?

Observance of the state's conditions of leisure work and materials.

The specific analysis is as follows:

h is an error, negative.

B false, water gas.

False, h should be negative.

d is correct, which is written inverted by the heat equation of the reaction.

A: Sure, right? This is a common method, but it may not be used in all cases.

b is used to determine the experimental formula, i.e., the ratio of the number of atoms of c, h, o.

c, NMR hydrogen spectroscopy is to determine the chemical environment of the hydrogen atom, for example, methane has only one peak, and its four Hs should be in exactly the same chemical environment.

d, don't explain.

In short, you have to figure out the intention of the questioner, understand?

Distillation can be distilled one by one according to the different boiling points, and the combustion is calculated according to the combustion products, and the proportion of elements such as C, H, O, N, etc.

b, of course, this is only an auxiliary identification: the corresponding analysis can be made according to the amount of water produced, carbon dioxide and oxygen consumed. Because of the production of water, the h,o is nothing more than the ** organic matter and oxygen, and then according to the amount of carbon dioxide generated.

It can be used as an effective method for determining the structure of organic matter!

A, it must be true, depending on the boiling point, it is distilled.

The average molecular formula of the gas mixture of C2H4 and C2H2 is C2Hy, then C2HY+(2+

Then 2 + solution gives y=

So yes. Solution x = choose b

and C2H4 are both 2 C, let a total of 1mol, then 2molCO2 is generated after combustion, there is, o is conserved, H2O is , then H is, addition is 1molC2H6, 6molH, so poor, it is necessary.

Assuming all the ethylene, it will be 3 times. Suppose all acetylene, to double. Cross to get ethylene to acetylene = 3:2

Assuming that the original 3mol ethylene and 2mol acetylene are originally required, 3mol hydrogen and 4mol hydrogen are required respectively. So a total of 7mol

Oxygen is sufficient, so there is no iron in the solid.

Limit method, let all FE2O3

then Fe2O3 8g is generated

Hence the inclusion of FEO

Whereas, with complete combustion, FEO does not exist alone, together with FE2O3 FE3O4 is formed, so the answer is C

The iron atom is.

The oxygen atom is. The ratio of ferric oxygen is greater than the proportion of Fe3O4, and the proportion of less than Fe2O3 is only consistent with C.

h2+cuo=cu+h2o △

x ( get x= combined.

The utilization rate of 50 is a total of H2 for the standard condition).

2)m→h2

Each m transfers 3 electrons, so it is a positive trivalent element, and its oxide is M2O3 with a mass fraction of 48 (2 m+48)=M=27, so M is an Al element.

1: , calculate the mass of oxygen in the cuo that reacts with hydrogen. From this, it is possible to know the consumption of hydrogen. It is also known that the hydrogen utilization rate is 50%, so there is a total of hydrogen, and the converted volume is.

2: Knowing that the relative atomic mass of oxygen is 16, let the metal be A2O3, then (16, so the relative atomic mass of the metal is 27, which is aluminum,

It is already known that there are 112 elements, which means that there are 112 types of atoms in nature.

Some elements also have isotopes, and the isotopes are different atoms between them, that is, there may be several atoms in one element.

Why is the mass of an atom 277 and the ratio of its atomic mass to the mass of 12c atom 277:12?

The mass of the atom, that is, the relative atomic mass of the atom, is 1 12 of the mass of the carbon 12 atom in terms of the mass ratio of the atom, that is, the ratio of the atomic mass to the mass of the 12c atom 1 12 is 277:1, then the ratio to the mass of the 12c atom is 277:12.

1. Each element may correspond to a variety of atoms, for example, hydrogen corresponds to three hydrogen atoms: deuterium, deuterium and tritium.

2. Mass number = atomic mass 12

H2S --- sulfur negative makes the cherry blossom bivalent.

SO2--- sulfur is four songs, and the remaining price of Tan potato.

s zero-valent neutralization reaction.

The transfer electron is, 4mol