lecture 26 - Turn on Camtasia Recording We have completed...

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Unformatted text preview: Turn on Camtasia Recording! We have completed chapter 17 and are moving on to chapter 18 18. ... 1 What is the common ion effect? A. The f t th t i i ti A Th fact that ionization of an acid or b f id base i is limited by the presence of it's conjugate base or acid. B. The principle that allows buffers to absorb acid or base without changing pH very much. C. C The interaction seen when HC3H5O3 and C C3H5O3- are in solution at the same time. D. A and C only E. All of the above ... 2 Citric acid has a Ka of 7.5 x 10-4. In what pH range is citric acid and its conjugate base a good buffer? A. pH 1.5-2.5 B. pH 2.5-3.5 C. pH 5.5-7.5 D. pH 7.5-8 E. pH 9-10 ... 3 Buffer Solutions Problem: What is the pH of a buffer that has [HOAc] = 0.700 M and [HOAc] [OAc-] = 0.600 M? HOAc + H2O OAc- + H3O+ Ka = 1.8 x 10-5 [HOAc] HOAc] [OAc-] [H3O+] equilib 0.700 - x 0.600 + x x Assuming that x << 0.700 and 0.600, we have g , K a = 1.8 x 10 -5 = [H3O+ ](0.600) 0.700 [H3O+] = 2.1 x 10-5 and pH = 4.68 ... 4 Buffer Solutions Notice that the expression for calculating the H+ conc. of the buffer is ... 5 HendersonHenderson-Hasselbalch Equation [H3O + ] = [Acid] Ka [Conj. base] Take th T k the negative l of both sides of thi ti log f b th id f this equation pH = pK a - log [Acid] [Conj. base] pH = pK a + log [Conj. [Conj base] [Acid] The pH is determined largely by the pKa of the acid and then adjusted by the ratio of acid and conjugate base. ... 6 What do you think is in the purple solution? A.An Acid B.A Base C.A salt D.Sea D S water t E.Boiled cabbage ... 7 Cabbage Water pH indicator-- anthocyanin pH pH pH pH pH p pH 2 4 6 8 10 12 red purple violet blue Blue-green g greenish yellow y ... 8 Indicators for Acid-Base Titrations Acid- ... 9 Natural Indicators Red rose extract at different pH's and with Al3+ ions Rose extract In CH3OH Add Al3+ Add HCl Add NH3 Add NH3/NH4+ See pages 848849 ... 10 Titrations pH Titrant volume, mL ... 11 ... 12 ... 13 ... 14 ... 15 ...
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