题目

取浓度相同的NaOH和HCl溶液，以3:2体积比相混合，所得溶液的pH等于12，则原溶液的浓度为(     ) A. 0.05 mol/L      B.0.07 mol/L     C. 0.01 mol/L      D.0.50 mol/L 答案：【答案】A 【解析】设原溶液物质的量浓度为cmol/L，V(NaOH)=3 L，V(HCl)=2 L，二者混合后反应，混合溶液体积为5 L，二者混合后反应，所得溶液pH=12，则 c(OH－)=10－2mol/L，3 L×cmol/L-2 L×cmol/L=10－2mol/L×5 L则c=0.05 mol/L；选C。听下面一段对话，回答第1-3题。 1. What did Mike do last night? A. He went to the police station. B. He drove into a drugstore and broke it up. C. He went shopping with his girlfriend. 2. Who did Mike have a quarrel with? A. A storekeeper. B. A policeman. C. His girlfriend.3. Where is Mike now?A. In a store. B. At the police station. C. At home.