Substance A has a pH of 5 and substance B has a pH of 7. Which of the following statements is correct?

Question

  Substance B is 20 times more acidic than substance A

 

  Substance A is 10 times more basic than substance B

 

  Substance A is twice as acidic as substance B

 

  Substance B is 100 times less acidic than substance A

 

Answer 1

Because pH is a log scale, each unit change in pH represents a 10-fold change in concentration of ,e.g. H+ ions (or OH- ions).

Thus comparing pH 5 to pH 7 represents a 100 fold difference so the last choice would be correct,  Substance B is 100 times less acidic than substance A