Question

1.	The approximate ionic strength of Lake Michigan is 3.55 mM and that of the Atlantic ocean is 0.707 M. For which solution would it be appropriate to calculate activity coefficients using the extended Debye-Hückel equation? A. Lake Michigan water B. Atlantic Ocean water C. both Lake Michigan and Atlantic Ocean water D. neither Lake Michigan nor Atlantic Ocean water
2.	For which solution would the activity coefficient of H+ have the smallest value? A. 0.010 M CaSO4 B. 0.025 M Na2SO4 C. 0.050 M NaCl D. deionized water
3.	In a solution with μ = 0.015 M, which ion would have the smallest value for activity coefficient? Briefly state why you selected this answer. A. K+ B. Cs+ C. H+ D. Na+

Answer 1

1.

Debye-Huckel equation works fairly well for lower concentrations that is ionic strength less than or equal to 0.1 M.

The ionic strength of both given solutions are greater than 0.1 M.

Answer: D. neither Lake Michigan nor Atlantic Ocean water

2):

The activity coefficient decreases as increasing ionic strength.

In the given solutions, the ionic strength of deionized water is smaller, the activity of H⁺ in this solution is smaller.

Answer: D. deionized water

3):

The activity coefficient decreases as the ionic size increases.

Since Cs⁺ is the larger in size, the activity coefficent of this ion is smaller.

Answer: B. Cs+