1. © University of South Carolina Board of Trustees pH of a Salt Solution I Determine the pH of a 0.589 M solution of NaNO 3.

2. © University of South Carolina Board of Trustees pH of a Salt Solution II Determine the pH of a 0.589 M solution of Na(CH 3 COO).

3. © University of South Carolina Board of Trustees pH of a Salt Solution II Determine the pH of a 0.589 M solution of Na(CH 3 COO). Determine the pH of a 0.589 M solution of CH 3 COO − (weak base). K a = 1.80 x10 -5 for CH 3 COOH.

4. © University of South Carolina Board of Trustees

5. K a K b = K w

6. © University of South Carolina Board of Trustees Chapt. 15 Acids and Bases Sec. 8 Molecular Structure and Acid Strength

7. H / A Size Mismatch (up–down periodic table) H–Br + H 2 O  Br − + H 3 O + vs H–F + H 2 O  F − + H 3 O + © University of South Carolina Board of Trustees HF better e − overlap Stronger HF bond Less likely to break HF less acidic

8. A Electronegativity: Primary Atom (left–right periodic table) © University of South Carolina Board of Trustees HOH + H 2 O  HO − + H 3 O + vs H-F + H 2 O  F − + H 3 O + F more electronegative F − more stable product More likely to form HF more acidic

9. A Electronegativity: Secondary Atoms (left–right periodic table) © University of South Carolina Board of Trustees HOH + H 2 O  H–O − + H 3 O + vs H 2 SO 4 + H 2 O  HSO 3 O − + H 3 O + SO 3 electronegative help stabilize O − More likely to form H 2 SO 4 more acidic

10. © University of South Carolina Board of Trustees Calculate the pH of a solution 0.20 M in NH 3 and 0.30 M in NH 4 Cl ( K b = 1.80 x10 −5 ). Calculate the pH of a 0.20 M solution of NH 3 ( K b = 1.80 x10 −5 ). Calculate the pH of a 0.30 M solution of NH 4 Cl ( K b = 1.80 x10 -5 ). Topic: Weak Base Weak Acid Weak Base + Conj. AcidWeak Base + Conj. Acid Buffer NH 4 Cl NH 4 + ( K b = 1.80 x10 −5 ).

11. © University of South Carolina Board of Trustees Chapt. 16 More Acids and Bases Sec. 3 Buffers

12. © University of South Carolina Board of Trustees Definition of Buffers Buffer Solution: ●Weak acid (base) + conj. base (acid) both present in similar concentrations ●Resists change in pH ●Simple, general formula

13. © University of South Carolina Board of Trustees Calculate the pH of a solution of 0.20 M NH 3 and 0.30 M NH 4 Cl ( K b = 1.80 x10 −5 ). pH of a Buffer: Example

14. © University of South Carolina Board of Trustees Student Example Calculate the pH of a buffer that is made from 0.125 mole of HCN ( K a = 4.9 x10 −10 ) and 0.075 mole of NaCN dissolved in 0.5 L of water.

15. © University of South Carolina Board of Trustees pH of a Buffer: Formula or