PROPERTIES OF ACIDS AND BASES

1. PROPERTIES OF ACIDS AND BASES

2. Acids • taste sour or tart (vinegar, lemons) • aqueous solutions of acids are electrolytes • cause indicators to change colors • many metals react with acids to produce H2 gas • react with hydroxides to form a salt and water • most formulas begin with H. • pH < 7, pOH > 7 • [H3O+] > 1.0 x 10-7, [OH-] < 1.0 x 10-7 • produce H3O+ (aka H+) ions in water solutions

3. Common uses of acids • HNO3 or HCl are used for etching metals. • HF is used for etching glass.

4. Bases • bitter taste (soap, unsweetened chocolate) • bases are electrolytes in aqueous solution • cause indicators to change colors • feel slippery • react with acids to form a salt and water • often contain OH- , or ammonia NH3 • pH > 7, pOH < 7 • [H3O+] < 1.0 x 10-7, [OH-] > 1.0 x 10-7 • produce OH- ions in water solutions

5. hydroxide ion (OH-) • formed when a water molecule loses a H+ • hydronium ion (H3O+) • formed when a water molecule gains a H+ H2O + H+ H3O+ *your text uses H+ and H3O+ interchangeably*

6. Acidic solutions [H3O+] > [OH-] [H3O+] > 1.0 x 10-7 Basic solutions [OH-] > [H3O+] [OH-] > 1.0 x 10-7 [H3O+] < 1.0 x 10-7

7. Acidic or Basic? • [H3O+] = 1 x 10-3 • [H3O+] = 1 x 10-11 • [OH-] = 1 x 10-4 • [OH-] = 1 x 10-13 H+ > 1.0 x 10-7 Acidic Basic H+ < 1.0 x 10-7 OH- > 1.0 x 10-7 Basic [H3O+] = 1 x 10-10 OH- < 1.0 x 10-7 Acidic [H3O+] = 1 x 10-1

8. pH Concept: pH = - log [H3O+] or - log [H+] • A logarithm (log) is the exponent to which 10 must be raised to get the number. • logbasevalue = exponent • If X = 10Y, then log10 X = Y • In calculator enter: - log (value)

9. Example: log 101 = 1 log 10-5 = -5 If [H3O+] = 1.0 x 10-4 pH = - log [H3O+] then pH = -log [1.0 x 10-4] = 4.00

10. pH problems: What is the pH if: [H3O+] = 1 x 10-5 pH = __________ pH = - log [H3O+] [H3O+] = 1 x 10-13 pH = __________ pH = - log [H3O+] pH > 7 is basic pH < 7 is acidic pH = 7 is neutral 5 Acidic 13 Basic

11. pOH = -log [OH-] What is the pOH if: [OH-] = 1 x 10-4 pOH = pOH = -log [OH-] [OH-] = 1 x 10-3 pOH = pOH = -log [OH-] 4 Basic 3 Basic

12. pH + pOH = 14 pH = 6 pOH = pH = 4 pOH = pOH = 3 pH = pOH = 11 pH = 8 10 11 3

13. Calculator: 10x (-pH.) [H3O+] = antilog (-pH)[OH-] = antilog (-pOH) • pH = 7.00 so [H3O+] = [H3O+] = antilog (-7.00) • pH = 3.00 [H3O+] = [H3O+] = antilog (-3.00) • pOH = 8.00 [OH-] = [H3O+] = [OH-] = antilog (-8.00) 14 = 8 + x x = 6 1.0 x 10-7 1.0 x 10-3 1.0 x 10-8 1.0 x 10-6

14. Using a programmable calculator for pH: What is the pH if [H3O+] = 5.2 x 10-2 pH = - log (H3O+) pH = (-) log (5.2 x 10-2) - log10 (5.2 x10-2) enter pH = 1.3

15. Using a programmable calculator for antilogs: What is the [H3O+] if the pH is 4.92? [H3O+] = antilog (-pH) [H3O+] = antilog (-4.92) Calculator: 10x (- 4.92) Enter [H3O+] = 10x is the 2nd function of the log key 1.2 x 10-5

16. Example: • pH = 9.29 [H3O+] = ? • [H3O+] = antilog (-pH) • [H3O+] = antilog (-9.29) • Calculator: • 10x(-9.29) Enter • [H3O+] = 5.13 x 10-10

17. Indicators • Indicators are substances that change color in solutions of different pH. • Indicators are usually weak acids. • They are one color in their acid form and a different color in their base form. • HIn  H+ + In- • Help determine approximate pH

18. Indicators cont. phenolphthalein • colorless in acid • pink in base • changes at pH 8.0 -10.0

19. Indicators cont. litmus • blue litmus turns red in acid • red turns blue in base universal indicator • mixture of indicators • changes into different colors at each pH (rainbow colors)

20. Indicators cont. bromothymol blue • blue in basic solutions • yellow in acidic solutions • green in neutral solutions

21. Common acidsCommon bases HCl NaOH HNO3 KOH H2SO4 Ca(OH)2 H3PO4 Mg(OH)2 HC2H3O2 NH3 H2CO3

22. Acid-Base Reactions • When acids and bases react, the products most commonly formed are water and a salt (ionic compound). • This is called a neutralizationreaction.