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Acids and Bases

Acids and Bases. Experimental Definitions. Acids Bases(alkalis) Turn blue litmus red Turn red litmus blue taste sour taste bitter corrode metals slippery feel Provide H+ ions Provide OH- ions Conducts electricity Conducts electricity .

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Acids and Bases

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  1. Acids and Bases

  2. Experimental Definitions • Acids Bases(alkalis) • Turn blue litmus red Turn red litmus blue • taste sour taste bitter • corrode metals slippery feel • Provide H+ ions Provide OH- ions • Conducts electricity Conducts electricity

  3. Various Definitions of Acids & Bases

  4. Arrhenius Definition • Acids release hydrogen ions in water: • HCl H2O H+ + Cl- • Bases release hydroxide ions in water: H2O Na+ + OH- NaOH

  5. An example of a Arrhenius Reaction • HCl(aq) + NaOH(aq) ---->Na+ + Cl- + OH- + H+ • ----------> NaCl (aq) + H2O(l) • This definition works for most simple examples, but there are some bases that do not release OH-. • Ammonia gas (NH3) is an example of a base that does not follow Arrhenius’ rule. • We need a new definition!!

  6. Brønsted - Lowry • Acids are PROTON DONORS • Bases are PROTON ACCEPTORS • When HCN Dissolves in water a reaction occurs: • HCN + H2O ----> H3O+ + CN- • HCN is a Bronsted Acid • Water is acting as a Bronsted Base.

  7. If a substance acts as a a proton donor and a proton acceptor it is said to be amphoteric.

  8. Conjugate acids and bases Conjugate acid-base pairs differ by a hydrogen ion. • HCN + H2O ----> H3O+ + CN- • Acidbaseconj. Acidconj. base

  9. Finding Conjugate Bases * Remove a hydrogen ion from the acid. • What would the conjugate bases be for the following 3 acids? • HI • NH4+ • HSO4- I- NH3 SO42-

  10. Finding Conjugate Acids * Add a hydrogen ion to the base. • What are the conjugate acids for the following bases? • SO42- • NH3 • C2H3O2- HSO4- NH4+ HC2H3O2

  11. Bronsted-Lowery’s limitations… • It would seem that Bronsted-Lowery is right on target, but there are some acids and bases out there that do not fit under either of our two sets of definitions. • Here are two reactions: • CaO(s) + SO2(g) ---> CaSO3(s) • H2SO3(aq) + Ca(OH)2(aq) ----> CaSO3(aq) + H2O • The second reaction is clearly a Bronsted-Lowery acid base reaction. BOTH reactions produce CaSO3 (a Base), so could the first reaction also be a acid-base reaction???? • We need another definition!!!

  12. Lewis Ex: NH3 + BCl3-----> H3NBCl3 • Lewis acids are electron pair acceptors • Lewis Bases are electron pair donors NH3 is the donor (Lewis base) and BCl3 is the acceptor (Lewis acid)

  13. Molarity • Molarity (M): - Measure of concentration - Defined as moles of solute per Liters of solution. - M = mol/L • Ex: What is the molarity of a solution obtained by dissolving 24.5g of H2SO4 in enough water to make 1.50L of solution?

  14. Molarity practice problems • 2. How many grams of Ca(OH)2 are there in 800.mL of a 2.0M Ca(OH)2 solution? • 3. What molarity of HNO3 solution would be needed if 35.0mL of acid were needed to neutralize 10.0mL of a 0.15M Mg(OH)2 solution? (Hint: write the balanced equation!) • 4. What is the molarity of an Fe(OH)3 solution if a 10.0mL sample was neutralized using 30.mL of a 0.20M HCl Solution? 0.167M 0.086 M 0.2 M

  15. Naming Acids: Binary acids • Binary acids: H + element • Format: • Hydro________ic acid • HCl = hydrochloric acid • Name the following Binary Acids: • HBr • H2S • HF • H3N hydrobromic acid hydrosulfuric acid hydrofluoric acid hydronitric acid

  16. Naming Acids: Ternary Acids • Ternary Acids = H + polyatomic anion. • Format • “ate”------> “ic” • “ite”-------> “ous” • H2SO4: • SO42- is “sulfate” • turn “ate” into “ic” • Sulfuric acid I "ate" something and it was "ic"ky. Mosquitos b"ite" "ous"!

  17. Name the following Ternary Acids • H2CrO4 • HNO3 • HClO4 • H3PO4 • HNO2 • HClO2 • HClO Chromic acid nitric acid perchloric acid phosphoric acid nitrous acid chlorous acid hypochlorous acid

  18. Neutralization • An Acid/ base reaction is called a neutralization reaction. • Double Displacement Reaction • Ex: NaOH + HCl --> NaCl +HOH • base + acid --> a salt + water

  19. Anhydrides • Anhydrides means “without water.” • Anhydrides can be: metallic or nonmetallic oxides (metals or nonmetals bonded to oxygen)

  20. A few formulas • Making an acid: • P2O5 + H2O -----> H3PO4 • Making a Base: • CaO + H2O -----> Ca(OH)2 Nonmetallic oxides make acids in water Metallic oxides make bases in water.

  21. Working with Anhydrides • Ex: What is the anhydride of H3PO4? • Step1: Write out all the atoms. If there is an ODD number of hydrogens, write it out TWICE. • HHHPOOOO • HHHPOOOO

  22. Anhydrides Cont. • Step2: Cross off “H2O”s until all hydrogens are gone. • HHHPOOOO • HHHPOOOO Step 3: The group of atoms leftover is the anhydride. P2O5

  23. Anhydrides of Bases • Ex: Determine the anhydride for Ca(OH)2. • CaOOHH CaO

  24. Anhydride Practice • Al(OH)3 • HNO3 • Mg(OH)2 • H2CO3 Al2O3 N2O5 MgO CO2

  25. Hydrolysis • Acid + Base ----> Salt + Water • The salt can be neutral, acidic or basic! • This is determined by the strength of the acid and base you started with.

  26. Solution Formed From Salt What does it mean to be strong?

  27. How do you tell if an acid is strong? • TEST #1: If the acid contains Oxygen • Subtract # hydrogens atoms from # oxygens atoms. • If the difference is < 2 acid is WEAK. • If the difference is >2 acid is STRONG. • Ex: H2SO4 4 -2 = 2--> strong acid H3PO4 4 - 3 = 1 --> weak acid • TEST #2: If the acid does not contain oxygen. • There are only 3 strong acids in this category. • HBr, HI, HCl

  28. How do you tell if a Base is Strong? • Bases: Metal ion + hydroxide ion. Metal comes from IA family or Ca, Ba, and Sr from family IIA.

  29. Hydrolysis Example 1 • Is the salt NaCl acidic basic or neutral when dissolved in water? • First figure out which acids and bases the salt came from • __acid___ +_base__ ----> NaCl + HOH HCL + NaOH ------> NaCl + HOH Strong strong neutral

  30. Hydrolysis- more Practice • Are each of the following salts acidic basic or neutral? • MgCO3 • Al(NO3)3 • CaSO4 basic acidic neutral

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