问答题
An acid-base indicator has a Ka of 3.0×10-5. The acid form of the indicator is red and the basic form is blue. By how much must the pH change in order to change the indicator from 75/% red to 75/% blue?
【正确答案】[H+]= Ka[acid]/[base] 75/% red:[H+]=(3.0×10-5)(75)/25=9.0×10-5 pH=4.05 75/% blue:[H+]=(3.0×10-5)(25)/75=1.0×10-5 pH=5.00 The change in pH is 5.00 - 4.05=0.95