问题
单项选择题
假设消毒时的细菌灭活速率与细菌个数为一级反应关系,消毒过程中,细菌数量从n0。减少到n0/2需要10s,则从n0/2减少到n0/4的时间是()。
A.5s
B.10s
C.20s
D.40s
答案
参考答案:B
解析:
据题意,反应器为PF型或CMB型。其模型查《考试教材》第1册表5—4,均为。式中k是反应常数,所以t仅与C0/Ci有关。由于,所以它们消耗的时间也相同。
假设消毒时的细菌灭活速率与细菌个数为一级反应关系,消毒过程中,细菌数量从n0。减少到n0/2需要10s,则从n0/2减少到n0/4的时间是()。
A.5s
B.10s
C.20s
D.40s
参考答案:B
解析:
据题意,反应器为PF型或CMB型。其模型查《考试教材》第1册表5—4,均为。式中k是反应常数,所以t仅与C0/Ci有关。由于,所以它们消耗的时间也相同。
Last spring, I was fortunate to be chosen to participate in an exchange study program. In my application letter, I was careful to 21 how much I wanted to see France; evidently, my excitement really came through in my words. Once I 22 that I was going, all I could think about was the fun of foreign travel and making all sorts of new and 23 friends. While traveling was inspiring and meeting people was 24 , nothing about my term in France was what I 25 . The moment I arrived in Paris, I was 26 by a nice French couple who would become my host parents. My entire experience was joyous and exciting 27 I received some shocking news from my program coordinator(协调人): there had been a death in my host parents’ extended family. They had to travel outside France for several weeks. That afternoon, I had to 28 out of one family’s house into another. The exchange coordinator told me I’d have a 29 this time and asked whether I could share a bedroom with an English speaker. To avoid the temptation(诱惑) to 30 my native language, I asked not to be 31 with an English-speaking roommate. When I got to my new room, I 32 myself to my new roommate Paolo, a Brazilian(巴西人) the same age as I, whom I was surprised to find playing one of my favorite CDS! In just a few hours, we knew we’d be good friends for the rest of the 33 . I left France with many 34 , so when people asked me what my favorite part of the trip was, they are always 35 to hear me talk about my Brazilian friend Paolo and scores of weekdays in class, weeknights on the town, and weekends 36 France we enjoyed together. I love how people 37 seem so different, but end up being so 38 . The most valuable lesson I gained from studying in France wasn’t just to respect the friend people 39 to respect all people, for your next best friend could be just a continent away. I would recommend an exchange program to anyone who wants to experience foreign cultures and gain meaningful 40 .
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