(20 1 1? Wuhu) Induction is an important learning method. Xiaohong summarized five chemical properties of hydrochloric acid when reviewing the properties of hydrochloric acid (as shown on the right,

(1) litmus will turn red when it meets acid solution, so purple litmus test solution will turn red when it drops into hydrochloric acid solution.

(2) Comprehensive analysis of the chemical properties of acid shows that hydrochloric acid can react with indicators, metal oxides, metals and salts, and also with alkali.

(3) The main component of rust is iron oxide, which reacts with hydrochloric acid to generate ferric chloride and water, so it can be written according to the writing requirements of chemical equations.

(4) The reaction between acid and salt must meet the conditions of double decomposition reaction, so the selected salt will generate water, gas or precipitate when it reacts with hydrochloric acid.

(5) The control variable method is to create the same external conditions. Therefore, in order to explore the reaction speed of magnesium, zinc and hydrochloric acid, the conditions that need to be controlled are the factors that may affect the reaction speed. According to the analysis, only the size of the container has no effect on the reaction speed.

So the answer is: (1) red (2) alkali (3) Fe2O3+6HCl = 2fecl3+3H2O (4) Na2CO3 (or AgNO3, etc. As long as it is reasonable) (5)ABD.