IX Acids Bases and Salts Behavior of many

IX. Acids, Bases and Salts

Behavior of many acids and bases can be explained by the Arrhenius theory. Arrhenius acids and bases are electrolytes. 2

An electrolyte is a substance which, when dissolved in water, forms a solution capable of conducting an electric current. The ability of a solution to conduct an electric current depends on the concentration of ions. Acids, Bases and Salts (ionic compounds) are electrolytes 3

Properties of Acids and Bases Acids ◦ ◦ ◦ Dissolve in water Electrolytes Taste sour Neutralize bases React with active metals to from hydrogen gas (H 2) ◦ Have a p. H less than 7 ◦ Turn blue litmus red Bases ◦ ◦ ◦ ◦ Dissolve in water Electrolytes Taste Bitter Neutralize acids Emulsify fats and oils Feel slippery Have a p. H more than 7 ◦ Turn red litmus blue 4

Regents Question: Which species can conduct an electric current? (1) Na. OH(s) Na. OH would conduct electricity if it was dissolved in water, not as a solid. (2) CH 3 OH(aq) CH OH is an alcohol, a non-electrolyte 3 (3) H 2 O(s) Water is a non-electrolyte, even as a liquid. (4) HCl(aq), hydrochloric acid is an electrolyte. 5

Regents Question: Which 0. 1 M solution contains an electrolyte? (1) C 6 H 12 O 6 (aq) (2) CH 3 COOH(aq) (3) CH 3 OH(aq) (4) CH 3 OCH 3 (aq) 6

Arrhenius acids yield H+ (aq), hydrogen ion as the only positive ion in an aqueous solution. The hydrogen ion may also be written as H 3 O+ (aq), hydronium ion. 7

Regents Question: An Arrhenius acid has (1) only hydroxide ions in solution (2) only hydrogen ions in solution (3) hydrogen ions as the only positive ions in solution (4) hydrogen ions as the only negative ions in solution 8

Regents Question: Which substance is an Arrhenius acid? (1) Li. F(aq) (2) HBr(aq) (3) Mg(OH)2 (aq) (4) CH 3 CHO 9

Table K lists the names and formulas of some common acids. Acids start with H An organic chemist would write the formula for acetic acid this way. A physical chemist would write the formula for acetic acid this way. 10

Arrhenius bases yield OH(aq), hydroxide ion as the only negative ion in an aqueous solution. 11

Regents Question: Which ion is produced when an Arrhenius base is dissolved in water? (1) H+ , as the only positive ion in solution (2) H 3 O+ , as the only positive ion in solution (3) OH– , as the only negative ion in solution (4) H– , as the only negative ion in solution 12

Table L lists the names and formulas of some common bases. 13

Ammonia is a base. When it dissolves in water, it produces hydroxide ions. NH 3(g) + H 2 O(l) (aq) NH 4+(aq) + OH- 14

In the process of neutralization, an Arrhenius acid an Arrhenius base react to form a salt and water. The Nonmetal from the acid combines with the metal from the base to make a salt. The H+ from the acid combines with the OH- from the base to make water (HOH = H 2 O). HCl(aq) + Na. OH(aq) Na. Cl(aq) + HOH H 2 SO 4(aq) + Ca(OH)2(aq) Ca. SO 4(aq) + 2 H 2 O Acid + Base Salt + Water 15

Regents Question: Given the reaction: HCl(aq) + Li. OH(aq) HOH(l)+ Li. Cl(aq) The reaction is best described as (1) neutralization (2) synthesis (3) decomposition (4) oxidation-reduction 16

Regents Question: Which equation represents a neutralization reaction? (1) Na 2 CO 3 + Ca. Cl 2 2 Na. Cl + Ca. CO 3 (2) Ni(NO 3)2 + H 2 S Ni. S + 2 HNO 3 (3) Na. Cl + Ag. NO 3 Ag. Cl + Na. NO 3 (4) H 2 SO 4 + Mg(OH)2 Mg. SO 4 + 2 H 2 O 17

Acid Nomenclature Review Binary Ternary An easy way to remember which goes with which… “In the cafeteria, you ATE something ICky”

Acid Nomenclature Flowchart (add acid at end)

Acid Nomenclature Review • HBr (aq) hydrobromic acid • H 2 CO 3 carbonic acid • H 2 SO 3 sulfurous acid

Name ‘Em! HI (aq) HCl (aq) H 2 SO 3 HNO 3 HIO 4

Titration is a laboratory process in which a volume of solution of known concentration is used to determine the concentration of another solution. Max. Va = Mbx. Vb Ma = Molarity of H+ Mb = Molarity of OH- Va = Volume of Acid Vb = Volume of Base At the equivalence point, the moles of H+ equals the moles of OH 22

Regents Question: When 50. milliliters of an HNO 3 solution is exactly neutralized by 150 milliliters of a 0. 50 M solution of KOH, what is the concentration of HNO 3 ? (1) 1. 0 M Use Ma. Va=Mb. Vb (2) 1. 5 M Ma=X (3) 3. 0 M Va=50. m. L (4) 0. 5 M Mb=0. 50 M Vb=150 m. L 23

Regents Question: If 5. 0 milliliters of a 0. 20 M HCl solution is required to neutralize exactly 10. milliliters of Na. OH, what is the concentration of the base? (1) 0. 10 M (2) 0. 20 M (3) 0. 30 M (4) 0. 40 M 24

Regents Question: A titration setup was used to determine the unknown molar concentration of a solution of Na. OH. A 1. 2 M HCl solution was used as the titration standard. The following data were collected. 35. 2 m. L - 23. 2 m. L 12. 0 m. L Calculate the volume of Na. OH solution used to neutralize 10. 0 m. L of the standard HCl solution in trial 3. Show your work. 25

Regents Question: According to Reference Table M, what indicator would be most appropriate in determining the end point of this titration? Give one reason for choosing this indicator. Bromthymol Blue because it changes color at a neutral p. H (7) Phenolphthalein because it changes color right after being neutral. Calculate the average molarity of the unknown Na. OH solution for all four trials. Your answer must include the correct number of significant figures and correct units. Ma. Va=Mb. Vb 1. 2 Mx 10. 0 m. L = X x 12. 2 m. L X=1. 0 M 1. 2 Mx 10. 0 m. L = X x 11. 0 m. L X=1. 1 M 1. 2 Mx 10. 0 m. L = X x 1 2. 0 m. L X=1. 0 M 1. 2 Mx 10. 0 m. L = X x 1 2. 5 m. L X=0. 96 M (1. 0 + 1. 1 + 1. 0 + 0. 96)/4 = 1. 015=1. 0 M 26

There alternate acid-base theories. One theory states that an acid is an H+ (proton) donor and a base is an H+ (proton) acceptor. When NH 3 reacts with HCl, the HCl donates a proton (H+) and NH 3 accepts a proton (H+) NH 3 + HCl NH 4+ + Cl- 27

The acidity or alkalinity of a solution can be measured by its p. H value. The relative level of acidity or alkalinity of a solution can be shown by using indicators. Red Litmus turns Blue in Base Blue Litmus turns Red in Acid 28

Table M lists some common acid -base indicators. 29

Color of Indicators at different p. Hs Indicator p. H 3 p. H 5 p. H 7 p. H 9 Methyl Orange red yellow Bromthymol Blue yellow green blue litmus red ? ? ? blue Bromcresol Green yellow green blue Thymol blue yellow green red When the p. H is lower than the lower number in the range, the color is the color on the left. When the p. H is higher than the higher number in the range, the color is the color on the right. When the p. H is between the two numbers in the range, the color is changing. 30

Regents Question: A compound whose water solution conducts electricity and turns phenolphthalein pink is (1) HCl (2) HC 2 H 3 O 2 (3) Na. OH (4) CH 3 OH 31

Regents Question: A student was given four unknown solutions. Each solution was checked for conductivity and tested with phenolphthalein. The results are shown in the data table below Based on the data table, which unknown solution could be 0. 1 M Na. OH? (1) A (2) B (3) C (4) D 32

Regents Question: A student is given two beakers, each containing an equal amount of clear, odorless liquid. One solution is acidic and the other is basic. a State two safe methods of distinguishing the acid solution from the base solution. 1 - Test with litmus paper 2 - Use a p. H meter b For each method, state the results of both the testing of the acid solution and the testing of the base solution. 1 - Red litmus paper would turn blue in base. Blue litmus paper would turn red in acid. 2 - The p. H of the acid would be below 7. The p. H of the base would be above 7. 33

On the p. H scale, each decrease of one unit of p. H represents a tenfold increase in hydronium ion concentration. [H 3 + O] =1 x -p. H 10 An acid with a p. H of 2 has 10 x the [H 3 O+] hydronium ion concentration as an acid with a p. H of 3. A base with a p. H of 10 has 100 x the [H 3 O+] hydronium ion concentration as a base with a 34 p. H of 12.

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Regents Question: Which of these 1 M solutions will have the highest p. H? (1) Na. OH is a base (2) CH 3 OH is an alcohol (3) HCl is an acid (4) Na. Cl is a salt 36

[H 3 O+] in decimal (mol/Liter) 1 x 10 0 0 0. 1 1 x 10 -1 1 0. 01 1 x 10 -2 2 0. 001 1 x 10 -3 3 0. 0001 1 x 10 -4 4 0. 00001 1 x 10 -5 5 0. 000001 1 x 10 -6 6 0. 0000001 1 x 10 -7 7 0. 00000001 1 x 10 -8 8 0. 00001 1 x 10 -9 9 0. 000001 1 x 10 -10 10 0. 000001 1 x 10 -11 11 0. 0000001 1 x 10 -12 12 0. 0000001 1 x 10 -13 13 0. 00000001 1 x 10 -14 14 Base 1. 0 Neutral p. H Acid [H 3 O+] in scientific notation (mol/Liter) 37

Simple p. H Calculations H+ Molarity Power of 10 p. H . 001 10 -3 3 Acid or Base? Acid . 00001 10 -5 5 Acid . 0000001 10 -7 7 neutral . 00001 10 -9 9 Base . 0000001 10 -12 12 Base . 00047 10 -3. 3 Acid

Regents Question: Four flasks each contain 100 milliliters of aqueous solutions of equal concentrations at 25°C and 1 atm. a Which solutions contain electrolytes? KCl, Ba(OH)2 and CH 3 COOH b Which solution has the lowest p. H? CH 3 COOH c What causes some aqueous solutions to have a low p. H? They are acids, they have dissolved hydrogen ions d Which solution is most likely to react with an Arrhenius acid to form a salt and water? Ba(OH)2 39

Conjugate Acids & Bases Any acid that can release H+ can re-accept and bind it to varying degrees. Strong acids like HCl release essentially all H+ ions. HCl H+ + Cl Weak acids like in vinegar release a small percentage of H+ ions. Most remain bound. HC 2 H 3 O 2 H+ + C 2 H 3 O 2 Salts contain positive & negative ions. Any negative ion has some capacity to bind with H+ ions to act like a base. Conjugates represent examples with or without H+ attached.

Conjugate Pairs

Equilibrium of Reversible Reactions Carbonated Water: CO 2(g) + H 2 O (l) H 2 CO 3(aq) H+(aq) + HCO 3 -(aq) Le Chatelier’s Principal – When disturbed a reaction will adjust to minimize the disturbance. (Teeter totter analogy) Carbonate pop by adding CO 2(g) pressure. CO 2(g) + H 2 O (l) H 2 CO 3(aq) Pop goes flat when container is opened! CO 2(g) + H 2 O (l) H 2 CO 3(aq)

Equilibrium Ratios x. A(aq) + y. B(aq) z. C(aq) Equilibrium Ratio (K) = products/reactants Keq = [C]z / [A]x[B]y Coefficients = exponents! Carbonated Water Equilibrium Ratio? Each reaction has a different equilibrium ratio value. Large ratios favor the _____, while small ratios favor the _____.