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原子量:H—1 N—14 O—16 Al—27 S— 32 K—39 Cl—35.5 Fe—56 Cu—64 一、选择题(共20分,每小题1分) 1.物质发生化学变化的本质特征是( )。 (A)颜色和状态发生了变化 (B)有放热和发光的现象发生 (C)有气体逸出 (D)有其它物质生成 2.下列物质中属于纯净物的是( )。 (A)经过除尘后的洁净空气 (B)由锰、氧、钾三种元素组成的高锰酸钾 (C)用氯酸钾和二氧化锰加热制取氧气后
Atomic weight: H—1 N—14 O—16 Al—27 S— 32 K—39 Cl—35.5 Fe—56 Cu—64 I. Multiple-choice questions (20 points in total, 1 point for each question) 1. Chemical change of substance The essential feature is (). (A) Changes in color and state (B) Exothermic and luminescent phenomena occur (C) Gas escapes (D) Other substances are generated 2. The following are pure substances (). (A) Clean air after dust removal (B) Potassium permanganate consisting of three elements of manganese, oxygen and potassium (C) After heating oxygen with potassium chlorate and manganese dioxide