patino_chm2046_chapter16

0 ml 0001 l 0100 mol hno 2 000400 mol hno 2 1 ml 1l

Info iconThis preview shows page 1. Sign up to view the full content.

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

Unformatted text preview: [Bz-], because half of At [HBz], initial moles of HBz has been converted to Bz− initial Therefore, [H3O+] = Ka = 6.3 x 10-5 pH = 4.20 = pKa of the acid A 40.0 mL sample of 0.100 M HNO2 is titrated with 0.200 M KOH. Calculate the pH after adding 5.00 mL KOH Write an equation for the rxn of KOH with HNO2. Determine the mol of acidbefore & mol of added KOH Make a stoichiometry table and determine the moles of HNO2 in excess and moles NO2− made HNO2 + OH− → NO2− + H2O 40.0 mL × 0.001 L 0.100 mol HNO 2 × = 0.00400 mol HNO 2 1 mL 1L 0.001 L 0.200 mol KOH 5.00 mL × × = 0.00100 mol KOH 1 mL 1L HNO2 mols before 0.00400 mols added -0.00100 mol reacted mols after NO2- OH− 0 ≈0 - 0.00100 +0.0010 -0.00100 0 0.00300 0.00100 ≈0 44 A 40.0 mL sample of 0.100 M HNO2 is titrated with 0.200 M KOH. Calculate the pH after adding 5.00 mL KOH. HNO2 + H2O ⇄ NO2− + H3O+ ( ) pK a = − log K a = − log 4.6 × 10 −4 = 3.15 Ka = 4.6 x 10-4 Write an equation for the reaction of HNO2 with H2O Determine Ka and pKa for HNO2 Use the HendersonHasselbalch eqn to determine the pH NO 2 − pH = pK a + log HNO 2 0.00100 pH = 3.15 + log = 2.67 0.00300 HNO2 NO2- OH− 0 ≈0 mols Before 0.00400 mols added 0.00100 mols After 0.00300 0.00100 ≈ 0 45 Titra tio n C urve s : Ac e tic a c id titra te d with Na O H T itra p H = 8 .7 Weak acid titrated with a strong Weak base base Strong acid (HCl) titrated with Strong acid (HCl) titrated with Strong a strong base (KOH) a strong base (KOH) Same for HCl + NaOH, and Same for HCl + NaOH, and HNO3 + KOH or NaOH HNO3 + KOH or NaOH Weak diprotic acid (H2C2O4) titrated with a (H titrated strong base (NaOH) strong Figure 18.7 Figure Weak base (NH3) Weak base (NH3 ) ttitrated with a strong itrated with a strong acid (HCl) or HNO3 acid (HCl) or HNO3 pH indicators pH An acid-base titration requires an acid-base indicator to determine the equivalence point. indicator This is usually an organic compound that is a weak acid or weak base (similar to dyes of flowers). (similar The aci...
View Full Document

Ask a homework question - tutors are online