百度作业网做PREP时遇到的数学难题,请牛人指教
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做PREP时遇到的数学难题,请牛人指教
1、The rate of a certain chemical reaction is directly proportaional 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%,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
1、The rate of a certain chemical reaction is directly proportaional 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%,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
第一题
关键词：
rate速度,proportional成比例的,concentration浓度,inversely相反地
反应速率＝k*(A^2)*(1/B)
B上升100%后,B'＝（1+100%）B＝2B
要反应速度不变,需要k*(A^2)*(1/B)＝k*(A'^2)*(1/B')
k约掉,B'代入,(A^2)*(1/B)＝(A'^2)*(1/2B)
B约掉,A’^2=2*(A^2)
两边开根号,A'=根号2*A
根号2＝1.414,故上涨40%
关键词：
rate速度,proportional成比例的,concentration浓度,inversely相反地
反应速率＝k*(A^2)*(1/B)
B上升100%后,B'＝（1+100%）B＝2B
要反应速度不变,需要k*(A^2)*(1/B)＝k*(A'^2)*(1/B')
k约掉,B'代入,(A^2)*(1/B)＝(A'^2)*(1/2B)
B约掉,A’^2=2*(A^2)
两边开根号,A'=根号2*A
根号2＝1.414,故上涨40%