(20 14? The knowledge of elements and their compounds in Xihua county is an important part of chemical research and learning. (1) Sodium chloride, calcium chloride and magnesium chloride are all contained. (1) According to the information of chlorine in the periodic table, it belongs to nonmetallic elements, and its atomic number is 17, that is, the number of protons is 17. There are 17 electrons outside the chlorine core and 7 electrons in the outermost layer, so it is easy to get an electron in the chemical reaction and become a chloride ion with unit negative charge. The relative atomic mass of this element is 35.45, but it is not "g" but "1", which is usually omitted.

(2) The salt-containing substance is sodium chloride, which consists of sodium ions and chloride ions;

(3) sodium bicarbonate is decomposed into sodium carbonate, water and carbon dioxide under heating conditions;

(4)① Add enough water to obtain a colorless and transparent solution, which means that there must be no copper sulfate; Adding enough hydrochloric acid produces bubbles, which means that there must be sodium carbonate, which can react with barium chloride to generate barium carbonate precipitate, while the solution obtained in I is transparent, which means that they cannot exist, so there must be no barium chloride; So far it can be judged that the possible substance is sodium hydroxide;

② It is sodium hydroxide that cannot be judged according to the experimental phenomenon, so the experiment can be designed according to the alkalinity of sodium hydroxide solution; Take a small amount of solution (I), add enough calcium chloride solution, let it stand, then take the supernatant and add phenolphthalein test solution dropwise. If the solution turns red, it means that it contains sodium hydroxide, otherwise it does not;

(5) let the mass of sodium carbonate in the soda ash sample be x.

Na2CO3+2HCl═2NaCl+H2O+CO2↑

106 44

x6.6g

10644=x6.6g

X =15.9g

The mass fraction of sodium carbonate in edible soda ash is:15.9g20g×100% = 79.5%.

So, the answer is: (1) d;

(2) Sodium ion and chloride ion; (3)2NaHCO3？ △? . ? na2co 3+H2O+CO2↑；

(4)① It must contain Na2CO3；; May contain NaOH；;

(2) Take a small amount of solution (I), add enough BaCl2 solution (or CaCl2 solution), let it stand, and take the supernatant and drop phenolphthalein solution (or measure the pH with pH test paper).

(5) solution: let the mass of sodium carbonate in the sample be x 。

Na2CO3+2HCl=2NaCl+H2O+CO2↑？

10644

x6.6g

10644=x6.6g

x═ 15.9？ g？

The mass fraction of sodium carbonate in edible soda ash is:15.9g20g×100%-79.5%.

A: The mass fraction of sodium carbonate in edible soda ash is 79.5%.