Wksht 3.3 Acid-Base Equilibria II Supplemental Instruction Iowa State University

Transcription

1 Wksht 3.3 Acid-Base Equilibria II Supplemental Instruction Iowa State University Leader: Deborah Course: CHEM 178 Instructor: Bonaccorsi/Vela Date: 2/13/18 1. What are the conjugate bases of a. HCO3 -? CO3 2- b. HBrO2? BrO2-2. What are the conjugate acids of a. SO4 2-? HSO4 - b. H2O? H3O + 3. List the 6 strong acids. HCl, HI, HBr, HClO4, HNO3, H2SO4 4. Write out the logarithmic equations for ph, poh, and pkw. ph = -log[h + ] poh = -log[oh - ] pkw = -log[h + ][OH - ] a. What is the equation for pkw in terms of poh and ph? pkw = ph + poh b. Given ph or poh, how do you determine [H + ] and [OH - ]? [H + ] = 10 -ph [OH - ] = 10 -poh 5. What is the poh of a solution with a ph of 3.67? If a sample of soil has a ph of 4.7, what is the H + concentration of the soil solution? 2.00 x 10-5 M 7. What is the concentration of OH - in a solution with an [H + ] of 3.56 x 10-4 M? 2.82 x M 8. Write the Bronsted-Lowry autoionization process of water. a. Complete the following table. Kw(50ºC) = 5.48 x 10-14

2 Neutral ph = 6.63 Acidic ph < 6.63 Basic ph > 6.63

3 Wksht 3.5 Acid-Base Equilibria III Supplemental Instruction Iowa State University Leader: Deborah Course: CHEM 178 Instructor: Bonaccorsi/Vela Date: 2/19/18 1. How can one determine the strength of a base given the Kb and pkb values? SB: Kb > 1 or pkb < 0 WB: Kb < 1 or pkb > 0 a. NH2OH: Kb = CH3NH2: Kb = 4.4 x 10-4 PH3: Kb = Calculate the pkbs of these bases then list them from strongest to weakest: CH3NH2 > NH2OH > PH3 2. Kw equals what in terms of Ka and Kb? Kw = Ka x Kb a. Complete the following acid-base equilibria reaction IO - (aq) + H2O (l) HIO (aq) + OH - (aq) The Ka of the conjugate acid is 2.3 x at 25 C. Calculate Kb(IO - ). Kb(IO - ) = 4.35 x Would you expect a 1.0 M NaNO3(aq) solution to be neutral, acidic, or basic at 25 C? neutral 4. Which of the following salts is expected to yield a basic solution when dissolved in water at 25 C? Select all that apply. a. NH4Cl b. KI c. Na2CO3 d. NaClO3 e. NaF 5. Calculate the ph of a 0.32 M H2SO4 (aq) solution at 298 K. ph = 0.49

4 Review: 6. Determine the reaction s rate law given the following information: XH4 + 2 O2 XO2 + 2 H2O Trial [XH4] (initial M) [O2] (initial M) Rate (M/s) Rate = k[xh4] 2 [O2] a. Find the rate constant value, with units. k = 57.8 M -2 s -1

5 Wksht 3.7 Acid-Base Equilibria cont. Supplemental Instruction Iowa State University Leader: Deborah Course: CHEM 178 Instructor: Bonaccorsi/Vela Date: 2/21/18 1. Write out the 2-stage dissociation process of H2SO4 in water. (1) H2SO4 (aq) + H2O (l) HSO4 - (aq) + H3O + (aq) (2) HSO4 - (aq) + H2O (l) SO4 2- (aq) + H3O + (aq) 2. Write out the 2-stage dissociation process of H2CrO4 in water. (Ka1 = 1.5 x 10-1, Ka2 = 3.2 x 10-7 ) (1) H2CrO4 (aq) + H2O (l) HCrO4 - (aq) + H3O + (aq) (2) HCrO4 - (aq) + H2O (l) CrO4 2- (aq) + H3O + (aq) a. Is NaHCrO4 a stronger acid or base in water at 298 K? stronger acid 3. a. Circle the protonated species. i. CN - ii. HCN b. Circle the deprotonated species. i. N3 - ii. HN3 c. What s one way we can set the ph of a solution? using buffers 4. The pka of HCNO is If the ph of three HCNO(aq) solutions are set to 3.70, 5.82, and 7, which species is more abundant in each solution, HCNO(aq) or CNO (aq)? ph of 3.70 equal ph of 5.82 CNO - ph of 7 CNO - 5. Calculate the ph of a 0.15 M solution of NH3. **Ka(conjugate acid) = 5.6 x ** ph = 11.21

6 Wksht 4.3 Aqueous Equilibria II Supplemental Instruction Iowa State University Leader: Deborah Course: CHEM 178 Instructor: Bonaccorsi/Vela Date: 2/28/18 1. Label the type of titration each graph represents and whether their equivalence point ph values would be greater than, equal to, or less than 7. WA being titrated by SB: ph at equivalence point > 7 SB being titrated by SA: ph at equivalence point

7 SA being titrated by SB: ph at equivalence point = 7 WB being titrated by SA: ph at equivalence point < 7 2. What is the solubility (in M; in g/ml) of Cu(OH)2 in water at 25 C? Ksp = and Cu(OH)2 = 99.4 g/mol. (Write the equilibrium equation when it s dissolved in water) 7.32 x 10-5 g/ml a. What is the ph of saturated Cu(OH)2 in water at 25 C? Find the molar solubility of Fe(OH)3 in water at 25 C. Ksp = 6.0 x x g/l a. What is its solubility (in g/l) under the same conditions? (Fe(OH)3 = g/mol) 2.32 x 10-8 g/l 4. What is the Qsp and Ksp in relation to each other for each of the following conditions? i. Solution in which precipitation occurs: Qsp > Ksp ii. Saturated solution: Qsp = Ksp iii. Unsaturated solution: Qsp < Ksp

8 b. Looking at the Ksp value for Fe(OH)3 in question 3, is Fe(OH)3 a soluble salt or a slightly soluble salt? slightly soluble 5. Calculate the ph of a saturated solution of Mn(OH)2. Ksp = 4.60 x a. Is Mn(OH)2(s) more soluble, less soluble, or equally soluble in a basic solution at 25 C? less soluble