英语周报2018到2022，外研答案

15.参孝答案BD说明分析A错误,草酸是二元弱酸,一级电离抑制二级电离,KaC(H). C(HC2O4) C(H).c(C2OXc(H2C2O4)”BC(HC2 O4Ka1>Ka2,当lgX=0时,pHgc(H)=-gK,pH1=1.22 K2=10,所以直线1中X表示的是HCO5,直线Ⅱ中X表示的是c(HC2Q)。B正确,pH=1.22的溶液中存在电荷守恒关系c(Na ) c(H )c(HC2O) 2(C2G) c(OH),溶液中(H )>c(OH),则c(HC2O) 2c(C2Q)>c(Na)。C错误当pH<419时,溶液中c(H)>10-41mo/C2 O4K(HC2OA) C(H<1,则c(HC2O4)>c(C2O-);当pH>1.22时,溶液中C(H)<10 1.22 mol/L,KaIK2H)·c(HC2O1)、c(H)·c(c(H2 C2 O)C(HC2 O4(H )·c(C2O-)cC2C)Kn·KC(H2C204'c(H2C2OA) C (H<1, c(H2 C2O)>C(C2O)D正确,pH=4.19的溶液中存在电荷守恒关系c(Na) c(H )=c(HC2Q) 2c(C2C) c(OH),溶液中c(HC2O)=c(C2O-),c(H )>c(OH),则3c(HC2O4)>c(Na )。

One possible versionSeveral minutes later, the ice broke suddenly and Harry's feet sank into the water. It was noep, but his legs got wet to the knees. Harry was so upset that the accident would delay hisschedule. He had to find some firewood to build a fire to dry his clothes. He pulled off his glovestook out his matches, and lighted the fire. Seeing the burning fire, he had thought he was safe. Butsuddenly, without warming, a heavy mass of snow dropped down. The flame of hope was put outUnluckily, his dog ran away and the fear of death came over Harry. He had no choice but torun to save himself. However, he did not feel his feet when they hit the ground. Having falleneveral times, he decided to rest a while. As he lay in the snow, he noticed he was not shaking. Hecould not feel his nose or fingers or feet. A feeling of horror came into his mind. It was when herealized he was going to die that he heard a bark and the noise his friends made

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