Chapter 16 Worksheet By Lauren Martin PDF

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CHEM 1052

Week 6.1

1. Calculate the pH of a buffer solution that is 0.200 M in HC2H3O2 and 0.200 M in NaC2H3O2. Ka = 1.8 x 10-5.

2. Calculate the pH of a buffer solution that is 0.060 M in benzoic acid (HC7H5O2) and 0.120 M in sodium benzoate (NaC7H5O2). For benzoic acid, Ka = 6.5 x 10-5.

3. A 1.0-L buffer solution contains 0.090 mol HC2H3O2 and 0.090 mol Na C2H3O2. The value of Ka for HC2H3O2 is 1.8 x 10-5. Since the initial amounts of acid and conjugate base are equal, the pH of the buffer is simply equal to pKa = -log (1.8 x 10-5) = 4.74. Calculate the new pH after adding 0.010 mol of solid NaOH to the buffer. For comparison, calculate the pH after adding 0.010 mol of solid NaOH to 1.0 L of pure water. (Ignore any small changes in volume that might occur upon addition of the base).

4. Use the Henderson-Hasselbalch equation to calculate the pH of a buffer solution that is 0.60 M in NH3 and 0.30 M in NH4Cl. For ammonia, pKb = 4.75.

5. Which acid (below) is the best choice to combine with the sodium salt of its conjugate base to make a solution buffered at pH 4.35? For the best choice, calculate the ratio of the conjugate base to the acid required to attain the desired pH. Chlorous acid (HClO2) pKa = 1.95 Formic acid (HCHO2) pKa = 3.74 Nitrous acid (HNO2) pKa = 3.34 Hypochlorous acid (HClO) pKa = 7.54

6. A 60.0-mL sample of a 0.150 M sodium hydroxide is titrated with 0.150 nitric acid. Calculate: a. The pH after adding 30.00 mL of HNO3 b. The pH at the equivalence point

7. Calculate the molar solubility of PbCl2 in pure water. For PbCl2, Ksp = 1.17 x 10-5.

8. The molar solubility of Ag2SO4 in pure water is 1.2 x 10-5 M. Calculate Ksp.

9. What is the molar solubility of CaF2 in a solution containing 0.200 M NaF? For CaF2, Ksp = 1.46 x 10-10.

10. A solution containing lead (II) nitrate is mixed with one containing sodium bromide to form a solution that is 0.0200 M in Pb(NO3)2 and 0.00400 M in NaBr. Does a precipitate form in the solution? For PbBr2, Ksp = 4.67 x 10-6....