用惰性电极电解2L1.0mol·L-1CuSO4溶液，在电路中通过0.5mol电子后，调换正负极继续电解，电路中又通过了1mo1电子，此时溶液中c(H+)(假设溶液体积不变)为（ ）
A．1.5mol·L-1
B．0.75mol·L-1
C．0.5mol·L-1
D．0.25mol·L-1
答案：C
调换正负极前后电极反应式如下：
调换前：阳极：4OH-―4e-
2H2O＋O2↑阴极：2Cu2+＋4e-2Cu
调换后：阳极：2Cu－4e-2Cu2+（先）4OH-―4e-2H2O＋O2↑（后） 阴极：2Cu2+＋4e-2Cu故电路中转移的1.5mol电子中，只有1mol由OH-放电产生，即消耗的n(OH-)1 mol，亦即溶液中积累的n(H+)="1" mol，则c(H+)=0.5mo1·L-1
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| I became lame (瘸的) in both legs in my childhood. Only in my wheelchair can I "walk". I still remember the 1 day at school. When I appeared (出现) at the door, everyone in the classroom looked at me in 2 . My face turned red. I wanted to run away from the room. It was the kindness and sympathy (同情) in their eyes that 3 me from doing so. I went shyly towards an empty seat. Being lame, I didn't dare (敢) to walk in front of my classmates. I was afraid that I might be 4 . In those days I was very sad to see others walking 5 . One day, a few students came up to me and asked me to go outside. I was really 6 . They encouraged me with a 7 smile and 8 me in ray wheelchair from place to place. I was thankful to them for. giving me a chance to 9 the sights (情景) of our lovely school with my own eyes. After that we often read, played and talked together. My friends were always ready to help me. It made me 10 I was crippled (残疾的). Once they asked me,"What is the most beautiful thing in our school?" Without hesitation(犹豫), I said, "It is the friendship." |
| ( )1. A. first ( )2. A. happiness ( )3. A. pretended ( )4. A. laughed at ( )5. A. quickly ( )6. A. sad ( )7. A. pretty ( )8. A. pushed ( )9. A. hear ( )10. A. forget | B. last B. sadness B. saved B. smiled at B. slowly B. surprised B. friendly B. placed B. see B. remember | C. second C. anger C. prevented C. watched at C. happily C. hurt C. exciting C. drew C. listen to C. imagine | D. next D. surprise D. treated D. talked of D. shyly D. nervous D. surprising. D. pulled D. draw D. think |