The rate of a certainchemical reaction is directly proportional to the square of the concentrationof chemical A present and inversely proportional to the concentration ofchemical B present. If the concentrationof chemical B is increased by   100 percent, which of the following is closest tothe percent change in the concentration of chemical A required to keep thereaction rate unchanged? 
100% decrease  
50% decrease  
40% decrease  
40% increase  
50% increase  
初始公式:r = kA^2 / B, Bdouble后 r = kA^2 / 2B, 维持不变, A也要乘以2才能上下抵消,平方1.4=1.96, 平方1.5=2.25, 明显1.4更接近2
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