1. ACIDS AND BASES Unit VII

2. I ELECTROLYTES  An electrolyte is a compound, that when dissolved in water, conducts electricity  How?  Ions (charges) produced are free to move  Movement of charge is conductivity  Examples  Acids  Bases  “Salts”  Soluble Ionic compounds

3. II PROPERTIES  Acids  Good conductors  Dissolve metals  Table J--Metals above “H 2 ” dissolve in acid  Taste sour  Turns litmus paper red  Turns phenolphthalein clear

4. II PROPERTIES  Bases  Good conductors  Dissolve fats  Feels slippery  Taste bitter  Turns litmus paper blue  Turns phenolphthalein pink

5. III DEFINITIONS A. Arrhenius  Acids  An Arrhenius acid contains H + ions  When dissolved in water these H + ions combine to form hydronium ion (H 3 O + )  Examples: HCl H 2 SO 4 HC 2 H 3 O 2  Bases  An Arrhenius base contains OH - ions (hydroxide ion) bonded to NH 4 + or a metal  Examples: NaOH Ca(OH) 2

6. III DEFINITIONS B. Brönsted-Lowry  Acids  A Brönsted-Lowry acid loses or donates protons to its conjugate (substance that differs by an H + )  HCl + NH 3 → Cl - + NH 4 +  HCl and Cl- are conjugate pairs; HCl is the acid and Cl - is its conjugate base  Bases  A Brönsted-Lowry base gains or accepts protons from its conjugate  HCl + NH 3 → Cl - + NH 4 +  NH 3 and NH 4 + are conjugate pairs; NH 3 is the base and NH 4 + is its conjugate acid

7. IV NOMENCLATURE A. Naming Compounds  Binary Acids  A binary acid contains hydrogen and a nonmetal  To name a binary acid  Use “hydro-”  Add nonmetal root word  End with “ic acid”  Ex. HCl  Hydrochloric acid  Ex. H 2 O  Hydroxic acid

8. IV NOMENCLATURE  Ternary Acids  A ternary acid contains hydrogen and a polyatomic ion  To name a ternary acid  Determine the polyatomic that is present using Reference Table E  If the polyatomic ion ends in “ate” change the ending to “ic”  If the polyatomic ion ends in “ite” change the ending to “ous”  Ex. HClO 3  Chlorate becomes Chloric acid (no hydro is used)  Ex. HNO 2  Nitrite becomes Nitrous acid

9. IV NOMENCLATURE  Bases  To name a base, name as you would any compound  Write the first element  Write the polyatomic  Add a Roman numeral if needed  Ex. NaOH  Sodium hydroxide  Ex. Cu(OH) 2  Copper II hydroxide

10. IV NOMENCLATURE B. Writing Formulas - Acids If binary Write H + and the other element present Assign charges and criss-cross  Ex. Hydrochloric acid H +1 Cl -1 HCl

11. IV NOMENCLATURE If ternary Identify the polyatomic present using ending Write H + and the polyatomic ion Assign charges and criss-cross Ex. Chloric acid chloric comes from chlorate ClO 3 -1 H +1 ClO 3 -1 HClO 3

12. V REACTIONS A Neutralization  Mixing of acid and base  HCl + NaOH →  Makes salt and water  Break (ionize) the acid and base  H +1 Cl -1 Na +1 OH -1  Join H to OH (H 2 O)  Join metal to nonmetal (assign charges and crisscross)  HCl + NaOH → H 2 O + NaCl

13.  Lab technique for neutralization is called Titration  Occurs when moles of acid equals moles of base  For 1:1 acid–base reactions  Moles acid = Moles base  M A V A = M B V B

14. EXAMPLES OF TITRATION PROBLEMS Given the balanced equation: HCl + NaOH → H 2 O + NaCl How many milliliters of 3.0M NaOH are needed to neutralize 20 milliliters of 2.5M HCl?  M B = 3.0M NaOH  M A = 2.5M HCl  V A = 20 mLs HCl  Ratio is 1:1 so M A V A = M B V B can be used  2.5M x 20 mLs = 3.0M x V B  50 = 3V B  V B =16.7 mLs NaOH

15. EXAMPLES OF TITRATION PROBLEMS Given the balanced equation: H 2 SO 4 + 2 NaOH → 2 H 2 O + Na 2 SO 4 How many milliliters of 1.2 M NaOH are needed to neutralize 23 milliliters of 1.9 M H 2 SO 4 ?  M B = 1.2 M NaOH  M A = 1.9 M H 2 SO 4  V A = 23 mLs H 2 SO 4  Ratio is NOT 1:1 so M A V A = M B V B CANNOT be used 23mL H 2 SO 4 x 1L x 1.9 mole H 2 SO 4 x 2 mole NaOH x 1L x 1000 ml 1000 mL 1 L 1 mole H 2 SO 4 1.2 mole NaOH 1L V B = 72.8 mLs NaOH

16. IV REACTIONS B Hydrolysis  Mixing of salt and water  Makes parent acid and base of the salt NaCl + HOH → HCl + NaOH  Reverse of neutralization

17. VI STRENGTH  Acid and base strength depend on number of ions in solution  More ions; stronger acid or base  Some acids ionize 100% (strongest acids)  HClHBrHI  H 2 SO 4 HNO 3 HClO 4  Some bases ionize 100% (strongest bases)  LiOHNaOHKOH  RbOHCsOHNH 4 OH

18. A. pH Every aqueous solution contains H + and OH - Acids have more H + than OH - Bases have more OH - than H + pH represents the amount of H + in a solution 1 7 14 Strong Weak Neutral Weak Strong acid acid base base Most H + Equal H + and OH - Least H + Least OH - Most OH -

19. pH Scale is logarithmic Values change by factors of 10 ex. pH = 3 vs. pH = 5 Difference in pH 2 units 10 x 10 pH 3 is 100 times stronger than pH 5 pH 5 is 1/100 th as strong as pH 3

20. B. Acid Base Indicators  Compounds that change color over pH ranges  Table M Common Acid–Base Indicators methyl orange 3.2–4.4 red to yellow bromthymol blue 6.0–7.6 yellow to blue phenolphthalein 8.2–10 colorless to pink litmus 5.5–8.2 red to blue bromcresol green 3.8–5.4 yellow to blue thymol blue 8.0–9.6 yellow to blue