CALCULATING THE pH OF A WEAK ACID If you were asked, say, to calculate the pH of a 0·010 mol l-1 solution of methanoic acid (a weak acid), you would use the relationship pH = pKa - log10 c, which is given on p.4 of the SQA Data Booklet. The pKa of methanoic acid is given as 3·75 on p. 13 of the SQA Data Booklet. So, substituting this value into the equation pH = pKa - log10 c gives pH = (3.75) - log10 0·010 = 1·875 - (-2) = or 2·875 2·88
CALCULATING THE pH OF A WEAK ACID If you were asked, say, to calculate the pH of a 0·010 mol l-1 solution of methanoic acid (a weak acid), you would use the relationship pH = pKa - log10 c, which is given on p.4 of the SQA Data Booklet. The pKa of methanoic acid is given as 3·75 on p. 13 of the SQA Data Booklet. So, substituting this value into the equation pH = pKa - log10 c gives pH = (3.75) - log10 0·010 = 1·875 - (-2) = 2·875 or 2·88
PhysicalChemistryVeryFinalNov16Nichola.docx