So the answer is: caso4+2nh4CO3 = CaCO3 ↓+(NH4) 2SO4+H2O+CO2 ↑;
(2) Adding KCl to (NH4) 2SO4 under the condition of drying and heating can generate easily decomposed ammonium chloride. When heated, ammonium chloride decomposes to generate hydrogen chloride and ammonia gas, and when the temperature is lowered, ammonium chloride is generated again, so that ammonium chloride can be separated and potassium sulfate can be obtained, and the reaction speed is accelerated; The method of separating CaSO4 _ 4 from the mixture obtained in reaction iv is to filter while it is hot, and the purpose of filtering while it is hot is to prevent KNO _ 3 from crystallizing and improve the yield of KNO _ 3.
So the answer is: separating NH4Cl from K2SO4 to accelerate the chemical reaction rate; Prevent potassium nitrate from crystallizing and improve the yield of potassium nitrate;
(3) To test whether KCl is mixed in K2SO4 obtained in reaction II, barium nitrate should be added first to completely convert potassium sulfate into barium sulfate precipitate, so as not to interfere with the detection of chloride ions, and then silver nitrate should be added to test potassium chloride. The operation method is to add Ba(NO3)2 solution until no precipitation occurs, let it stand, and then drop AgNO3 solution into the supernatant. If there is precipitation, it means that KCl is mixed in K2SO4.
So the answer is: add Ba(NO3)2 solution until no precipitation occurs, let it stand, and drop AgNO3 solution into the supernatant. If there is precipitation, KCl；; Mix in K2SO4;
(4) In the whole process, besides (NH4)2SO4, there are also CaSO4 and KNO3, so the answers are: CaSO4 and Kno3;
(5)B is a triatomic molecule, and B reacts with O2 to generate 1 volume gas A and 2 volumes of red-brown gas C, where C should be NO2 and yellow-green gas should be Cl2.
Then B contains elements N and Cl, and the reaction equation should be 2B+O2=Cl2+2NO2, so the molecular formula of B is NOCl.
So the answer is: NOCl. ..