Answer to Question #174709 in General Chemistry for Mitra

Question

Question about Electrochemical 
 a) Assume that you have measured the pH of an aqueous solution to 3.72 +/- 0.2. Calculate the activity of the oxonium ion in the aqueous solution and the uncertainty in the activity. 

b) What factors are the reason why the pH cannot be determined with great accuracy, at low or high pH?

c) When using an ion-selective electrode containing lanthanum fluoride crystal to determine the fluoride content, a concentrated buffer with a pH between 5 and 8 is usually added to all solutions. Describe in detail three (3) main reasons for this

Answer 1

a) $K_w=1.0×10 ^{-4}$

b) Glass membrane.

Diaphragms.

Reference electrolyte

Reference electrode.

Measurement medium.

c) The ion-selective electrode works based on the principle of a galvanic cell. ... The transport of ions from an area of high concentration to low concentration, through the selective binding of ions with the specific sites of the membrane, creates a potential difference.