Why is the electrometric method of pH determination more accurate than the colorimetric method?

A standard solution contains 100 ppm of Fe, which was found to have an absorbance of 0.151 au at 508 nm after the addition of 1,10-phenanthroline, pH 4 buffer, and hydroxylamine. Then, a water sample treated similarly exhibited an absorbance of 0.109 au. Which of the following statements is true?   The Fe concentration of the water sample is higher than 100 ppm.   It is impossible to estimate the Fe content of the water sample from information presented.   The Fe concentration of the water sample is lower than 100 ppm.   The Fe concentration of the water sample is equal to 100 ppm.

Ivan B. Garcia A. What is the acid/base ratio? Why is it important in the titrimetric process? B. Why should you boil the sample solution right before reaching the end point? c. Does the primary standard used for the standardization of HCI fit the criteria for a good primary standard? Why or Why not?

A 370.00 mL solution of 0.00190 M AB5 is added to a 200.00 mL solution of 0.00165 M CD2. What is pQsp for AD5?