# Assigned problems _8, answers - Chemistry 2080 Spring 2011...

This preview shows pages 1–2. Sign up to view the full content.

Chemistry 2080 Spring 2011 Problem Set #8 - due date: Friday April 8th at 2 pm Name:________________ Lab TA Name:__________________ Lab Day/Time:______________________ 1) (a) Calculate the pH of a 1.3x10 -7 M solution of benzoic acid at 25°C. (The pKa of benzoic acid is 4.19 at 25°C. You may have to take into account the autoionization of water). (b) What is the percent ionization of the benzoic acid in this 1.3x10 -7 M solution at 25°C? We will use the abbreviation BzOH for benzoic acid, and BzO for the benzoate anion. The relevant chemical equation is: BzOH + H 2 O BzO + H 3 O + We have: K a = [BzO ][H 3 O + ] / [BzOH] = 10 -4.19 = 6.46 x 10 -5 . . . . . . . . . . . . . . . (1) Material balance: [BzOH total ] = [BzO ] + [BzOH] = 1.3 x 10 –7 M . . . . . . . . (2) We also have: K w = [H 3 O + ][OH ] = 1.00 x 10 –14 (at 25°C) . . . . . . . . . . . . (3) and the requirement of electroneutrality: [H 3 O + ] = [OH ] + [BzO ] . . . . . . . (4) So we have 4 equations in the 4 unknowns:

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

### Page1 / 2

Assigned problems _8, answers - Chemistry 2080 Spring 2011...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online