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Unit 10- Acids and Bases

Unit 10- Acids and Bases. Acidity Alkalinity Arrhenius acid Arrhenius base Bronsted-Lowry acid Bronsted-Lowry base Buffer Electrolyte. Hydrogen ion Hydronium ion Indicator Neutralization pH scale Salt Titration. Properties of Acids. Have sour taste

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Unit 10- Acids and Bases

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  1. Unit 10- Acids and Bases • Acidity • Alkalinity • Arrhenius acid • Arrhenius base • Bronsted-Lowry acid • Bronsted-Lowry base • Buffer • Electrolyte • Hydrogen ion • Hydronium ion • Indicator • Neutralization • pH scale • Salt • Titration

  2. Properties of Acids • Have sour taste • ***take my word, don’t taste lab chemicals • Can conduct electric current in solution • Electrolytes • Good conductor= strong acid • Poor conductor= weak acid • Turns blue litmus paper red “blue to red a-cid” • Most common acids are liquid or gas • React with metals to produce H2 gas • Above H2 in Table J will react (single-replacement) • React with bases to form salt and water • Neutralization (double-replacement • Can generate hydronium ions H3O+ in water • pH less than 7

  3. Acids • Sulfuric- car batteries • Ascorbic- tomatoes

  4. Properties of Bases • Have bitter taste • ***take my word, don’t taste lab chemicals • Can conduct electric current in solution • Electrolytes • Good conductor= strong base • Poor conductor= weak base • Most common bases are solid • React with acids to form salt and water • Neutralization (double-replacement • Can generate hydroxide ions OH- in water • Turns red litmus paper blue “blue base” • pH greater than 7

  5. Bases • Sodium bicarbonate

  6. Acid and Base Strength • Due to degree of ionization • Complete dissociation-strong acid or base

  7. Definitions of Acids and Bases • Arrhenius Theory- • Arrhenius acid- produces H+ or H3O+ as the only positive ions in solution • Hydrogen ions will attract to water molecule and form hydronium ions • Arrhenius base- produces OH- ions in solution • Except!!! Not all bases have OH- ions • Drawbacks: • Limited to aqueous solutions • Can’t classify amphoteric substances (substances that act as bases and acids)

  8. Arrhenius acid is a substance that produces H+ (H3O+) in water Arrhenius base is a substance that produces OH- in water

  9. A Brønsted-Lowry acid is a proton donor A Brønsted-Lowry base is a proton acceptor Definitions of Acids and Bases con’t • BrØnsted-LowryTheory- • B-L acid- proton donor • B-L base- proton acceptor • Proton = hydrogen ion that has lost its electron conjugateacid conjugatebase acid base

  10. Definitions of Acids and Bases con’t • All Arrhenius acids are also B-L acids • B-L bases expand the substances that can be considered bases

  11. Naming acids • If an acid molecule forms 1 H ion it’s a: • Monoprotic acid (HCl) • If an acid molecule forms 2 H ions it’s a: • Diprotic acid (H2SO4) • If an acid molecule forms 3 H ions it’s a: • Triprotic acid (H3PO4)

  12. Naming acids con’t • For binary acids: • Hydro + element name – ine + ic + acid • Ex: HCl- hydrochloric acid • Try HF- _________________________ • For ternary acids:containing H, O and another element • 3rd element name, modify to end in –ic or –ous + acid • Ex: HNO3- nitric acid nitrogen –ogen + ic + acid • Try HNO2- _____________________

  13. Naming bases No oxygen  • Name of positive ion + hydroxide • Ex: Ba(OH)2- barium hydroxide • Try KOH- ____________________ More oxygen  Less oxygen 

  14. Reactions with acids and bases • Acids and metals- • Use Table J in Ref Tables • Acid will react with anything above H2 • Single replacement rx’s Zn(s) + 2HCl(aq)  H2(g) + ZnCl2(aq) • Neutralization reactions- • Arrhenius acid + Arrhenius base  salt + water • Equivalence pt- pt at which neutralization is complete; when H30+ ion = OH- ions

  15. Neutralization Rx • Words: Hydrochloric acid + sodium hydroxide  water + sodium chloride • Chemical formulas: HCl(aq) + NaOH(aq)  H2O(l) + NaCl(aq) • Ions: H+(aq) + Cl-(aq) + Na+(aq) + OH-(aq)  H2O(l) + Na+(aq) + Cl-(aq) • Omitting spectator ions: H+(aq) + OH-(aq)  H2O(l) or H3O+(aq)+ OH-(aq)  2H2O(l)

  16. Neutralization Rx’s con’t • Diprotic acid + dihydroxy base makes 2 water molecules • Ex: Ca(OH)2 + H2SO4 2H2O + CaSO4 • Acids and bases with unequal H+ and OH- needs to be balanced • Ex: ___Mg(OH)2 + __HCl  __H2O + ___MgCl2 (two) (one) • Salts produced- ionic substance with a metal and nonmetal or polyatomic ion

  17. Titrations • Process of adding a measured volume of an acid or base of known concentration to an acid or base of unknown concentration until neutralization occurs • Cacid x Vacid = Cbase x Vbase (known) (known) = (unknown) (known) molarity x volume = molarity x volume • Standard solution= soln of known concentration • There needs to be a 1:1 ratio of H+ to OH- • Diprotic ex: 2.5M H2SO4 = 5M H+ • Triprotic ex: 2MH3PO4 = 6M H+ • Dihydroxy base ex: .5MBa(OH)2 = 1M OH-

  18. Acidity and Alkalinity of Solutions • Relative strength of an acid or base in terms of their H+ or OH- concentrations • H2O  H+ + OH- • Le Chateliers principle [H+] = [OH-] • If one increases the other decreases • If you add HCl to water H+ increases so it becomes more acidic

  19. pH scale • Expresses the strength of acids and bases • Instead of using very small numbers, we just use the NEGATIVE power of 10 on the Molarity of the H+ (or OH-) ion. • pH change of 1 is a 10 fold increase or decrease in ions

  20. pH indicators • Substance that changes its color when it gains or loses a proton (H+ ion) • Universal indicators are a mix of a few indicators • pH meter- electric instrument with probes sensitive to H3O+ creates voltage between probes

  21. Buffers • Solutions that resist change in pH • Weak acid or base • Usually a weak acid and its conjugate base • Stabilizes pH • Foods, shampoo, antacids, blood

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