Therefore, filling: remove insoluble impurities in the raw salt.
Through steps ③ and ④, soluble impurities CaCl2 _ 2 and MgCl _ 2 in the crude salt can be removed.
Therefore, filling: removing soluble impurities CaCl2 _ 2 and MgCl _ 2 from the original salt.
(2) The name of experimental operation X is filtration, and the glass instruments used in this operation include beaker, glass rod, funnel, etc.
Therefore, fill in: filter; chimney
(3) The main purpose of the experimental step (3) is to remove magnesium chloride, and sodium hydroxide reacts with magnesium chloride to generate magnesium hydroxide precipitate and sodium chloride. The chemical equation of the reaction is: magnesium chloride +2 sodium hydroxide/magnesium hydroxide+2 sodium chloride.
Therefore, fill in: MgCl2+2 NaOH ═ Mg (OH) 2 ↓+2 NaCl.
The way to judge the excess of sodium hydroxide solution is to take a little sample, add it into the test tube, and add phenolphthalein test solution dropwise, and the solution will turn red.
So, filling: take a few samples, add them to the test tube, and add phenolphthalein test solution dropwise, and the solution will turn red.
(4) The precipitate D produced in the experimental step (4) is calcium carbonate.
So fill in: calcium carbonate.
(5) Experimental Step ⑤ Salt crystals are obtained by evaporating the solvent instead of lowering the temperature of the solution, because the solubility of sodium chloride is less affected by temperature.
Therefore, the solubility of sodium chloride is less affected by temperature.
In the process of evaporating salt solution, stir the solution with a glass rod to avoid splashing droplets due to local overheating.
Therefore, filling: stir the solution to avoid splashing droplets due to local overheating.
(6) This method is not feasible, because MgCO3 and Ca(OH)2 are slightly soluble, and only one reagent will produce a slightly soluble impurity, which cannot be completely removed.
Therefore, fill in: not feasible; MgCO3 and Ca(OH)2 are slightly soluble, and only one reagent will produce slightly soluble impurities, which cannot be completely removed.
(7) The evaluation is based on the new impurities NaOH and Na2CO3 when MgCl2 and CaCl2 are removed. Be introduced.
Therefore, when MgCl2 and CaCl2 are removed, NaOH and Na2CO3 are new impurities. Be introduced.
(8) The designed experiment is to add dilute hydrochloric acid to solution C drop by drop until no bubbles are generated. When phenolphthalein test solution is added drop by drop, the solution does not change color.
Therefore, filling: dilute hydrochloric acid is added to solution C drop by drop until bubbles are no longer generated. When phenolphthalein test solution is added drop by drop, the solution does not change color.