．用两支惰性电极插入500mL AgNO3溶液中，通电电解。当电解液的c（H＋）从1×10－6mol·L－1变为1×10－3mol·L－1时（设电解时阴极没有氢气析出且电解液在电解前后体积变化可以忽略不计），电极上析出银的质量约是（ ）
A．27mg
B．54mg
C．108mg
D．216mg
答案：B
c（H＋）从1×10－6mol·L－1变为1×10－3mol·L－1时，1×10－6mol·L－1太小可忽略不计。 4AgNO3 ＋ 2H2O 
4Ag ＋ O2↑＋ 4HNO3
4×108g 4
x 1×10－3mol·L－1×0.5L
解之，得：x ＝ 54mg
| 完形填空。 | |||
| The Best Holiday I was unbelievably proud of my nine-year-old daughter, Emily. 1 to buy a mountain bike, she'd been saving her pocket money all year, as well as doing small jobs to earn extra money. By Thanksgiving , she had collected only $49. I said, " You 2 have your pick from my bicycle 3 ". "Thanks, Daddy. But your bikes are so old. " She was right. All my girls' bikes were 1950s models , not the kind a kid today would 4 choose. As Christmas 5 near, Emily and I went bike shopping . As we left one store, she 6 a Salvation Army volunteer standing next to a big pot. "Can we give something, Daddy?" She asked. "Sorry, Em, I'm out of 7 . " Throughout December, Emily continued to work hard. Then one day, she made a 8 announcement. "You know all the money I've been saving?" she said hesitantly. "I'm going to give it to the poor people. " So one cold morning before Christmas, Emily handed her total savings of $58 to a volunteer who was really very 9 . 10 by Emily's selflessness, I decided to contribute 11 of my old bicycles to a car dealer who was collecting used bikes for poor children. 12 I selected a shiny model from my collection, however, it seemed as if a second bike took on a glow. Should I contribute two? No, one would be enough. But I couldn't 13 the feeling that I should give a second bike. When I later 14 the bikes, the car dealer said, "You're making two kids very 15 , sir . Here are your tickets. For each bicycle contributed, we're 16 away one chance to win a girl's mountain bike. " Why wasn't I surprised when that second ticket proved to be the 17 ? I like to think it was God's way of 18 a little girl for a sacrifice 19 her year--while giving her dad a lesson in the 20 . | |||
| ( )1.A. Promised ( )2.A. need ( )3.A. collection ( )4.A. seldom ( )5.A. drew ( )6.A. observed ( )7.A. work ( )8.A. disappointing ( )9.A. agreeable ( )10.A. Moved ( )11.A. one ( )12.A. While ( )13.A. express ( )14.A. returned ( )15.A. sweet ( )16.A. putting ( )17.A. present ( )18.A. greeting ( )19.A. under ( )20.A. process | B. Amazed B. should B. contribution B. likely B. became B. sensed B. charge B. surprising B. hopeful B. Shocked B. some B. As B. describe B. delivered B. healthy B. giving B. harvest B. praising B. before B. project | C. Determined C. must C. shop C. slightly C. went C. watched C. time C. formal C. thankful C. Persuaded C. two C. Because C. explain C. chose C. happy C. storing C. winner C. sheltering C. beyond C. struggle | D. Organized D. can D. club D. merely D. pulled D. noticed D. change D. public D. pitiful D. Demanded D. any D. Though D. shake D. shared D. fair D. signing D. chance D. rewarding D. within D. communication |