Prep ps1-142

wuhaiyaner

没看懂

142.      14580-!-item-!-187;#058&010013

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?

 

 

(A) 100% decrease

(B) 50% decrease

(C) 40% decrease

(D) 40% increase

(E) 50% increase

hedongshi

 某化学反应的速率与化学物质A浓度的平方正相关，与化学物质B的浓度负相关。若B的浓度增加了100%，为了使反应速率不变，A应该变化多少

答案是D吗

zouweiyao

A^2/B,与A的平方成正比,与B成反比,B增加100% A^2/2B等于原来A^2/B,所以A要增加

到根号2倍的A,所以是1.414,大约增加40%,答案是C

我以前也遇到该题,迷糊了半天,论坛一位大牛给解的.也分享给你了