How can one distinguish between acids, bases, and salts?

Electrolytes: Form ions in waterForm ions in water Aqueous solutions can conduct electricityAqueous solutions can conduct electricity Salts: Ionic Compounds Ionic Compounds May Include Polyatomic IonsMay Include Polyatomic Ions M + to NM -M + to NM - Acids: pH < 7 pH < 7 [H + ] > [OH - ][H + ] > [OH - ] Bases: pH > 7 pH > 7 [OH - ] > [H + ][OH - ] > [H + ]

Memorize… An acid and a base react to form a salt and waterAn acid and a base react to form a salt and water Called a neutralization reactionCalled a neutralization reaction HCl (aq) + NaOH (aq)  NaCl (aq) + H 2 O (l)HCl (aq) + NaOH (aq)  NaCl (aq) + H 2 O (l)

Look in Reference Table for Common Acids and Bases! Ask me how to recognize acids / bases / salts

Characteristics of Acids and Bases: Taste sour (vinegar, lemons) Electrolytes in solution React with some metals to produce H 2 (g) Mg + HCl  MgCl 2 + H 2 (SR reaction) Taste bitter Feel slippery Electrolytes in solution

Arrhenius Theory Definitions: A substance that when dissolved in water produces the H + (aq) ion as the only positive ion in solution. Ex. HCl(aq)  H + + Cl - A substance that when dissolved in water produces the OH - (aq) ion as the only negative ion in solution. Ex. NaOH(aq)  Na + + OH -

Bronsted-Lowry Theory Definitions: Based on the proton (H + ) A proton donor. Must release the H + (aq) ion. Ex. Ex. HCl + H 2 O  H 3 O + + Cl - A proton acceptor. Does not need to have the OH - (aq) ion, but must have a lone pair of electrons. Ex. Ex. NH 3 +H 2 O  NH OH -

1) If the acid not an oxoacid: (includes all binary acids) Start with the prefix hydro- followed by the root of the anion and the suffix -ic, and add the word acid. Ex. HCl – hydrochloric acid HI – hydroiodic acid H 2 S – hydrosulfuric acid hydro____ic acid. 2) If the acid is an oxoacid: (the anion is a polyatomic ion containing the element oxygen) Start with the root of the central atom in the polyatomic ion (Table E) and add the appropriate suffix followed by the word acid. Suffix:-ate  -ic -ite  -ous Ex.H 2 SO 4 – sulfuric acid H 2 SO 3 – sulfurous acid HClO – hypochlorous acid

Strong Acids or Bases: Strong Acids: HClHCl HBrHBr HIHI HClO 4HClO 4 H 2 SO 4H 2 SO 4 HNO 3HNO 3 Strong Bases: Group 1 or Group 2 metal bonded to OH - ion.Group 1 or Group 2 metal bonded to OH - ion. Ex: NaOH, Mg(OH) 2Ex: NaOH, Mg(OH) 2 Consider everything else to be weak!

Can only donate ONE proton (H+ ion) Ex. HCl, HNO 3, HClO 3, HCN, HC 2 H 3 O 2 Can donate more than one proton (H+ ion) Diprotic acids can donate up to two protons Ex. H2SO4, H2CO3 Triprotic acids can donate up to three protons Ex. H3PO4

Can act either as an acid or a base Water is a common amphoteric substance. H 2 O(l) + H 2 O(l) H 3 O + (aq) + OH - (aq) One water molecule acts as an acid while the other acts as a base. Hydrogen sulfate is another amphoteric substance. In an acidic environment with excess protons, HSO 4 - will act as a base and accept a proton.In an acidic environment with excess protons, HSO 4 - will act as a base and accept a proton. In a basic environment, HSO 4 - can act as an acid and donate a proton.In a basic environment, HSO 4 - can act as an acid and donate a proton.

Share the same core and differ by ONE H+ ion (proton) Ex. If HCl is the acid, what is its conjugate base? Ex. In the forward reaction, what is the acid? HNO 3 + NH 3  NO NH 4 + What is its conjugate base? Ex. What is the conjugate acid of HSO4-? Ex. What is the conjugate acid of SO42-? Remember Bronsted-Lowry: Acid is H + donor, base is H + acceptor

H 2 SO 4 (aq) + NH 3 (aq) HSO 4 - (aq) + NH 4 + (aq) For the forward reaction, what is the Bronsted acid? (consider which species donates a proton in the forward reaction) For the reverse reaction, what is the Bronsted acid? What species from the forward and reverse reactions are the Bronsted bases? List both conjugate acid-base pairs.

Based on the H+ ion concentration in an aqueous solution pH = - log [H+] If the concentration of H+ ions is 1 x 10-4 M, what is the pH? If the concentration of H+ ions is 1 x 10-8 M, what is the pH? pH = 7, neutral pH < 7, acidic pH > 7, basic

pH = - log [H + ] A decrease of one unit of the pH scale represents a ten-fold increase (x 10) in the H+ ion concentration. If the pH of a lake decreased due to acid rain from 6 in 1997 to 4 in 2007, how many times greater is the H+ ion concentration in 2007 compared to the H+ ion concentration in 1997?

The concentration of the H + ion is related to the concentration of the OH - ion. Water molecules ionize to a certain extent: For pure water, [H+] = [OH-] = 1 x M pH = 7, pOH = 7 H2O  H+ + OH- Then, [H + ] x [OH - ] = 1 x = K w (a constant) For all aqueous solutions, [H + ] x [OH - ] = K w, so [H + ] x [OH - ] = 1 x , and pH + pOH = 14. What is the pH of a solution that has a hydroxide ion concentration of 1 x 10-4 M? pOH = - log [OH - ]

“See-Saw Diagram”

Salts can be neutral, acidic or basic: Original Acid: Original Base: Resulting Salt: StrongStrongNeutral StrongWeakAcidic WeakStrongBasic WeakWeak ?? (College)

(for Arrhenius acids and bases) The reaction between an acid and a base yields a salt and water. ++ Ex. HCl(aq) + NaOH(aq)  NaCl(aq) + H2O(l) Ex. What are the products of a reaction between sulfuric acid and calcium hydroxide? Ex. What acid and base were used in a neutralization reaction that produced the salt barium chlorate?

In order to be a neutral solution, pH = 7 and pOH =7. Also, [H+] = [OH-] = 1 x 10-7 M In other words, a neutral solution has the same number of moles of H + ions as OH - ions. Titration equation (when there is a neutralization between an acid and abase): MaVa ia = MbVb ib (use any unit of volume as long as you’re consistent) iarepresents the number of H+ ions from the acid ib represents the number of OH- ions from the base

In an acid-base titration experiment, one determines the concentration of an acid or base through neutralization. What is i a if you use 1 M phosphoric acid? What is i b if you use 1 M calcium hydroxide? Use the titration equation: M a V a i a = M b V b i b

Practice Titration Problems: How many mL of 0.45 M HCl will neutralize 25.0 mL of 1.00 M KOH? What is the molarity of HNO 3 if 25.0 mL is completely neutralized by 12.5 mL of standard 0.50 M NaOH? What is the concentration of H 2 SO 4 if 25 mL of the acid is completely neutralized by 18 mL of standard 1.0 M NaOH?

Acid-Base Indicators are used to provide information about the pH of solutions. Also, the indicators can help determine the endpoint (point of neutralization) of an acid-base titration. Use the pH Range and Color Change Columns together. Below the range, the color is given on the left, and above the range, the color is given on the right. What is the color of litmus in a solution that has a pH of 4.0? pH of 9.0?

What is the color of the following indicators in a solution that has a pH of 5.0? Methyl Orange – Bromthymol Blue – Phenolphthalein – Litmus - What could be the pH of a solution when methyl orange is yellow, phenolphthalein is colorless, bromcresol green is blue, and thymol blue is yellow? 1, 4, 7, or 11?

In the laboratory, phenolphthalein is often used to approximate the endpoint of a titration. Notice that the color change is from colorless to pink. Thus, it is easy to note when the color change occurs. Phenolphthalein was added to the acid in the flask, and a standard base drips from the buret. The titration is finished, or the endpoint is reached, when the pink color persists in the mixed solution.