In order to test whether a Ba OH 2 crystal deteriorates after being placed in air

The chemical equation for choosing DBA(OH)2 to deteriorate in air is as follows.

ba(oh)2 + co2 == baco3↓ +h2o

Add hydrochloric acid or nitric acid, if there are bubbles, it proves that there is BaCO3, proves that Ba(OH)2 has deteriorated, if there are no bubbles, there is no deterioration, the equation is as follows:

baco3 + 2hcl == bacl2 + h2o +co2↑

baco3 + 2hno3 == ba(no3)2 + h2o +co2↑

ab is doable.

Add water, Ba(OH)2 is soluble in water, BaCO3 is insoluble in water, if there is white solid remaining insoluble, it has deteriorated, if not, it has not deteriorated.

c Feasible. d is not feasible, even if ba(oh)2 does not deteriorate, there is a white solid remaining, because.

ba(oh)2 + na2so4 == baso4↓ +2naoh

Ba(OH)2 meets CO2 in the air to form BAC3, BACO3 can react with A to produce bubbles, while BA(OH)2 cannot.

BaCO3 can react with B to produce bubbles, while Ba(OH)2 cannot.

Ba(OH)2 is soluble in water while BaCO3 cannot.

BaCO3 is insoluble in D and forms a precipitate; The reaction of Ba(OH)2 with D also forms a precipitate.

So choose D

A Add BaCl2 solution, produce white precipitate, may be AgCl precipitate, can not rule out the interference of Cl-, hydrochloric acid should be added to acidify first, if there is no phenomenon, then add barium chloride solution, so A is wrong;

b may contain HCO3 and can also produce carbon dioxide gas, so b is false;

c Add water to dissolve and add hydrochloric acid to exclude SO3

2-, such as precipitation, indicates that part of it has been oxidized and deteriorated, so c is correct;

d The gas that can make the wet potassium iodide starch test paper blue should be an oxidizing gas, but not necessarily Cl2, so D is wrong

Therefore, C

ba（oh）2·nh2o =ba（oh）2 + nh2o171+18n 171（171+18n）：：

n = impurities do not decompose, and impurities n value is not accurate.

This reaction is not a redox reaction, the valency of ammonium ions and nitrogen in ammonia is -3 valence, and the file is actually a compound decomposition reaction, strong alkali and salt generate weak alkali and salt, weak alkali ammonia monohydrate is unstable, and ammonia and water socks are decomposed.

ba(oh)2·8h2o+2nh4cl==2nh3+10h2o+bacl2

Quicklime reacts with water to release heat, which belongs to exothermic reaction;

NH4Cl crystals with Ba(Oh)2?8H2O mixing and stirring to absorb the heat of the stool, which belongs to the endothermic reaction;

Acetic acid ionization absorbs heat and is an endothermic reaction;

Solid sodium hydroxide dissolves in water and releases heat, but it is a physical change;

H2 is burned in Cl2 and releases heat, which is an exothermic reaction.

The concentrated H2SO4 dilutes the heat released, but it is a physical change.

The acid-base neutralization reaction releases heat, which is an exothermic reaction; Hand Linghu.

Therefore, choose B

Analysis of mountain oak: a pure substance decomposes into NH3, H2O and CO2 when heated slightlySo A must be NH4HCO3

Because A pure substance is decomposed into NH3, H2O and CO2 when heated slightly, then there are four elements in A, C, H N O, which may be NH4HCO3 or (NH4)2CO3, and NH4HCO3 can only decompose when it is heated slightly, while (NH4)2CO3 can decompose at a higher temperature. So A must be NH4HCO3

NH4HCO3 = Heating = NH3 (CO2( )H2ONh4)2CO3 = High Temperature = 2NH3 (CO2( )H2O

A. The mixing reaction of Ba(OH)2 crystal and NH4Cl crystal is endothermic reaction, so A is correct;

B. H2 and O2 can be obtained by electrolysis of water, which is a decomposition reaction and belongs to an endothermic reaction, so C is wrong;

c. The essence of endothermic reaction is that the total energy of the reactant is lower than the total energy of the product, which has nothing to do with the conditions, and some exothermic reactions also need to be heated, such as the combustion of charcoal is an exothermic reaction, but it needs to be ignited, and the purpose of ignition is to make it reach the ignition point, and then the thermite reaction is also, so C is wrong;

d. The essence of exothermic reaction is that the total energy of the reactants is greater than the total energy of the products, so D is wrong;

So choose A

3 All c

Option A contains either silver ions or SO3

2- There is also this phenomenon, item A is wrong; Option B may also contain HSO3- and HCO3

Sodium sulfite is partially oxidized to sodium sulfate, hydrochloric acid is added to produce gas, and barium chloride is added to produce precipitation, option c is correct; Cl2, br2, O3, etc. can make the wet starch potassium iodide test strip blue, and the D item is wrong.