Honors Chemistry

Chapters 15 & 16 Study Questions

(Use tables in Chapters 14 and 15 as needed.)

 

1. Compare the following titration curves with respect to i) steepness of curve at equivalence, ii) pH at the start of the titration, iii) pH at equivalence, iv) is there buffer at half-equivalence:

a) strong acid titrated with strong base. b) weak acid titrated with strong base.

c) weak base titrated with strong acid.

 

2. Use Figure 15.8, page 749, as needed to answer the following:

a) What is the color of bromthymol blue at pH 9?

b) At what pH is methyl red orange?

c) What is the Ka of an indicator that changes color at pH 3.5?

d) What is a good indicator to use when titrating sodium nitrite (NaNO2) with HCl?

 

3. How many ml of 2.00 M HNO3 would be required to neutralize 12.5 ml of 0.0800 M NH3? (optional: What is the pH of the resulting solution?)

 

4. Amy wants to prepare a buffer with a pH of 5.00.

a) What ratio of CH3COO-/CH3COOH does she need?

b) How could she mix 0.100 M CH3COOH and 0.100 M NaCH3COO to make this buffer?

c) How could she make this buffer using 0.100 M CH3COOH and 0.100 M NaOH?

d) Name another buffer system she could use.

 

5. What is the pH of a solution made by mixing

a) 750 ml of 0.400 M NaOH and 250 ml of 0.800 M HCl?

b) 100 ml of 0.100 M NaHCO3 and 200 ml 0.100 M H2CO3? (Ka for H2CO3 is 4.4 x 10-7)

 

6. The solubility of MgCl2 at 25C is approximately 8.0 g MgCl2/100 g water. Assuming the solution has a density of 1.00 g/cm3, calculate the concentration of MgCl2 in a saturated solution in moles/liter and then calculate Ksp for MgCl2.

 

7. The Ksp for CuCrO4 is 3.6 x 10-6. What is the molarity of a saturated solution of CuCrO4?

 

8. Silver nitrate (AgNO3) is added to a solution of 0.020 M sodium carbonate. At what concentration of AgNO3 does a precipitate start to form?

 

9. A solution is prepared by mixing 50.0 ml of 0.0100 M lead(II) nitrate with 50.0 ml of 0.0200 M sodium bromide. Will a precipitate form?

 

10. Write balanced chemical equations for

a) the reaction when strong acid is added to H2CO3/NaHCO3 buffer.

b) the ionization in water of silver phosphate. Write an expression for Ksp for this reaction.

 

11. What is the molar mass of an acid if 0.422 g of the acid are neutralized by 17.5 mL of 0.268 M NaOH?

 

Summary of Chapters 15 & 16: Applications of Aqueous Equilibria

 

acid-base reactions

buffers

how they work

significance of pKa of buffer

Henderson-Hasselbach equation

calculations relating [A]/[HA] to pH

how to prepare buffers

acid-base titrations

equivalence point

shape of titration curves

relation of strength of acid or base to pH

of equivalence point

pH indicators

relevance of pKa of indicator

Ksp

expression for Ksp

calculations of equilibrium

concentrations from Ksp and vice versa

relationship to extent of solubility

calculations of concentrations of ions that form precipitates

common ion effect