P1-PS-13

由拎 » 2008-05-16 14:55

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 increased by 100%, which of the following is closet to the percentage change in the concentration of chemical A required to keep the reaction unchanged?

(A) 100% decrease

(B) 50% decrease

(C) 40% decreasee

(D) 40% increase

(E) 50% increase

ANS: (D)

請問有人可以幫我解答嗎?? 謝謝!! :smile

由 **canadacom_orig** » 2008-05-16 15:12

題目意思是說化學物A的平方與此化學反應速率成正比

化學物B 與此化學反應速率成反比

所以B增加100% 換句話說B變成了兩倍所以反應速率變成1/2

要讓原本的速率不變所以A勢必要增加能讓速度變成兩倍去抵銷那1/2倍
得到算式會是2*1/2=1

A的平方與速率成正比所以A平方就等於2 A就等於根號2=1.41...

換句話說增加了40%左右