11-18-08[lecture19]jl - Chem 116/18/08(JL(a and(d goes...

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Unformatted text preview: Chem 116 Lecture 19 11/18/08 (JL) (a) and (d) goes together, and (b) and (c) goes together. Acid: (b) and (d) Base: (a) and (c) 2. Does equilibrium lies primarily to the right or to the left? …HPO2‐ is base. HCO3‐ and H2PO4‐ are acid You need to know which acid is stronger. ‐Bigger Ka on left => Equilibrium lies on the right. ‐Bigger Ka on right => Equilibrium lies on the left. Therefore, equilibrium lies primarily to the left. • Equilibrium doesn’t necessarily have to be at pH7. Equilibrium= moles of acid is equal to moles of base. (a) Strong base (Arrhenius base) NaOH when added to water completely dissociates 1 mol NaOH to water ‐> 1 mol Na+ and 1 mol OH‐ 0.0012M OH‐ solution. [OH‐] = 0.0012M pOH = ‐log(0.0012) = 2.92 pH + pOH = 14 =>pH = 14 – 2.92 =11.08 …check sig.fig. (b) pH = 10.46 Goal: Get the concentration of Sr(OH)2. Find concentration of [OH‐]. Get that from pOH Get pOH from the pH pOH = 14 – pH = 14 – 10.46 ‐ –pOH ‐3.54 [OH ] = 10 = 10 = 0.000288M 0.000288 (mol OH‐ / L) × (1 mol Sr(OH)2 = (2 mol OH‐) = 3.54 0.00014M is the Sr(OH)2 concentration. ...
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