大家帮忙看两道prep题吧.. 谢！！！

medyhui · 发表于 2010-10-20 20:55:08

The rate of a certain chemical reaction is directly proportional to the square of the concentration of chemical A present and inversely proportional to the concentration of chemical B present. If the concentration of chemical B is increased by 100 percent, which of the following is closest to the percent change in the concentration of chemical A required to keep the reaction rate unchanged?
答案是40%increase..

还有一道
一个表在附件里
问m+n等于多少
答案是5

完全不明白~ 纠结了好久大家帮忙看下吧...

shihang0724 · 发表于 2010-10-20 21:04:32

x=(A^2)/B
=（（根号2）*A）^2/(2B)

故增加了141.4%

BlackTTea · 发表于 2010-10-20 21:08:40

第一题，The rate of a certain chemical reaction可以表示成KA^2/B（与A浓度的平方成正比，与B浓度呈反比），即求KA^2/B=K(xA)^2/2B，解出来x=1.414，所以A要增加大约40%。
第二题，由图可知，m=z+4, n=y+e m+n=z+4+y+e, 而z+e=10, y+4=-5，所以m+n=5

medyhui · 发表于 2010-10-21 10:15:32

明白了明白了~ 谢谢啊哈哈~ ls的不解释的话我完全都看不懂那个表啥意思.. 太聪明了哈哈

大家帮忙看两道prep题吧.. 谢！！！

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