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Unformatted text preview: Ch. 14-15: Acids, Bases and Solubility AP Review Questions **On AP test, if in doubt use 3 significant digits. It is always correct. **For logs: If K a = 1.8 X10-5 , then pK a = 4.7932685. K a has two significant digits. pK a should be 4.79, since the 4 tells the power (the 7,9 are significant.) ** For strong acids: #Oxygens - # Hydrogens is 2 or greater. H 2 SO 4 strong, H 2 SO 3 weak, HIO 3 strong etc. ** Acid strength increases with the number of oxygens. (The more oxygens, the better the negative charge can be supported and be made stable when the H + leaves.) **Molarity = mol / L = mmol / ml ** For buffer solutions the weak acid must have a pKa within one pH unit of the desired buffer pH. **In titrations: At the halfway point to equivalency HA will equal A- HA + OH- ↔ H 2 O + A – 1.0M 0.5M -0.5-0.5 +0.5 0.5 0.5 pH = pK a + log {[A- ] / [HA]} pH = pK a At the equivalence point : for strong acids : the titration curve is steep and the equivalence point equals pH = 7. (strong acids and strong bases completely neutralize one another to make a neutral pH of 7.) but for weak acids/weak bases : the titration curve has less of a steepness (it is flatter) and the equivalence point is determined by stoichiometry and the dissociation of the weak acid/ weak base, not by pH. It will not be neutral! (see textbook p. 696-716) {The pH at the equivalence point of a weak acid with a strong base is always greater than 7 , because the anion of the acid (that is left in solution) is a base. The weaker the acid, the higher the pH at the equivalence point. The pH at the equivalence point of a weak base with a strong acid will be less than 7 , since the hydrated base is acidic. The weaker the base, the lower the pH at the equivalence point .} 1) Which pair of substances cannot be the major components of (coexist in) an aqueous solution? a) OH- and H + b) H 2 PO 4- and HPO 4 2- c) HOCl and OCl- d) SO 4 2- and SO 3 2- e) H 2 CO 3 and CO 3 2- 2) Each of the following can act as both a Bronsted acid and a Bronsted base EXCEPT a) HSO 4- b) H 2 PO 4- c) NH 4 + d) H 2 O e) HCO 3- 3) Which of the following anion(s) is/are not derived from a strong acid? I. F 1- II. NO 3 1- III. HS-1 IV. ClO 4 1- V. C 2 H 3 O 2 1- a) V only b) I, II, and III only c) I, II, and IV only d) I, III, V only e) II and IV only 4) Which of the following is not a conjugate acid- base pair? a) H 2 SO 4 and SO 4 2- b) HCl and Cl- c) NH 3 and NH 2- d) HPO 4 2- and PO 4 3- e) H 2 S and HS- 5) Which of the following is a Lewis Theory Acid? a) NH 3 b) CO 2 c) CH 4 d) BH 3 e) LiH 6) Which of the following can function as both a Bronsted-Lowry acid and a Bronsted-Lowry base? a) HCl b) H 2 SO 4 c) HSO 3- d) SO 4 2- e) H + 7) In the reaction CO 3 2- + H 2 O ↔ HCO 3- + OH- the carbonate ion is a a) Bronsted acid b) Lewis acid c) Arrhenius acid d) Bronsted base e) Arrhenius base 8) Which of the following is the strongest acid in water?...
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