chem 5 - PROPERTIES OF ACIDS l. Sour taste 2. Corrosive a)...

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Unformatted text preview: PROPERTIES OF ACIDS l. Sour taste 2. Corrosive a) React with active metals to release hydrogen gas. Zn + 2 HCE —> ZnCt’2 + Hug) b) React with metal carbonates and with metal bicarbonates to release carbon dioxide gas. 2HCE. + NaZCO3 —> 2NaCB + H20 + com) HCE + NaHCO3 —> NaCl’ + H20 + COM) 3. Litmus is red in the presence of acid. 4. Phenolphthalein is colorless in the presence of acid. 5. React with bases to cancel each other’s properties. Arrhenius Acid - releases H1+ in aqueous solution HCB —> H1+ + Cfl' But a hydrogen ion is such an intensely positive concentration of charge that it cannot exist free in the solution. It will combine with the polar water molecule to form the hydronium ion, H3O”. To recognize this, a broader definition of acids is needed. Bronsted-Lowry Acid - a proton donor HCf + H20 —> H3O1+ + CE“ HC2H3O2 + H20 2 H3O1+ + C2H3021‘ PROPERTIES OF BASES Bitter taste Slippery feel Caustic or corrosive Litmus is blue in the presence of base. Phenolphthalein is magenta in the presence of base. Bases neutralize acids. .O‘P‘PP’PE‘ Arrhenius Base — dissociates in aqueous solution to release hydroxide ions NaOH —> Na” + OHl' Bronsted-Lowry Base - a proton acceptor NH3 + H20 2 NH.1+ + OHl' page 95 Acid solution has [HH] > [OH] Base solution has [HH] < [OHI‘] Neutral solution has [H”] = [OH] In water, there always is an equilibrium between water molecules and hydrogen and hydroxide ions. That equilibrium represents the ionization of water molecules. Remembering that we do not represent the concentrations of liquids in equilibrium calculations, and remembering that the value of the ionization constant, Kw, for water is 1.00 x 10'”: H20“) :2 HHW + OH1'(aq) I 0 0 C —-- +x +x E -—- x x K = [H“] [0H1'] = 1.00 x 10'14 M2 W X =1.00 x 10‘7M = [H“] = [OH1'] Acid solution has [HH] > 1.00 x 10‘7 M and [OH] < 1.00 x 10‘7 M Base solution has [OH] > 1.00 x 10'7 M and [HH] < 1.00 x 10'7 M Neutral solution has [HH] = [OH] = 1.00 x 10'7 M pH = -log[H1+] 1. What is the pH in a solution having a hydrogen ion concentration of 1.00 x 10'7 M? pH = 7 Acid solution has 0 _<_ pH < 7, base solution has 7 > pH _>_ 14, neutral soluton has pH = 7. 2. What is the pH of a solution having each of the following hydrogen ion concentrations? a) 3.64 x 10'3 M b) 5.71 x 10'6 M c) 8.93 x 10'9 M a) pH = —log(3.64 X 103) = 2.439 b) pH = -10g(5.71 x 106) = 5.243 c) pH = -log(8.93 x109) = 8.049 page 96 pH = -log[H1+] = —log[H3O”] pOH = -log[OH1‘] pZn = —log[Zn2+] pKeq 2 '10g(Keq) In aqueous solution, pH + pOH = 14 3. Find the hydrogen ion concentration and the hydroxide ion concentration in a soluton that has a pH of 4.74. pH = —log[H‘+] 4.74 = —log[H1+] [HH] = antilog(-4.74) = 10-474 = 1.8x10‘5M To find [OHl‘]: [H‘+][OH1'] = 1.00x10'14M2 (1.8 x 10‘5 M) [OH] = 1.00 x 10'14 M2 [OHI'] = 5.6 x 10'10 M OR pH + pOH = 14 4.74 + pOH = 14 pOH = 9.26 [OH] = antilog(-9.26) = 109'26 = 5.5 x 10'10 M 4. Find the hydrogen ion concentration and the hydroxide ion concentration in a soltuion that has a pH of 8.75. [HH] = 10“"75 = 1.8 x 10'9 M (1.8 x 10'9 M) [OH] = 1.00 x 10’14 M2 [OH] = 5.6 X 10‘6 M STRONG ACID pH CALCULATIONS 5. Determine the pH of 0.250 M HCt’. Since hydrochloric acid is a strong acid, it is completely ionized. That means that all of the original acid undergoes ionization and gets used by the ionization reaction. When we are asked for a pH, that means its value after the reaction has either reached completion or reached equilibrium, so it means using the hydrogen ion concentration from the "E" line of the ICE diagram. Hce (aq) "’ H1+(aq) + Cf 1taco I 0.250 M 0 0 C —0.250 M +0250 M +0250 M E 0 0.250 M 0.250 M pH = -log(0.250) = 0.602 page 97 ...
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This note was uploaded on 02/05/2011 for the course CALCULUS/C 202 taught by Professor Tadius during the Spring '11 term at Benedictine KS.

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chem 5 - PROPERTIES OF ACIDS l. Sour taste 2. Corrosive a)...

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