Question

For each of the scenarios, determine if the ionic strength of the solution would increase, decrease, or not change. Ignore any effects caused by the change in volume.

1) If a solution of HNO3 were added to a solution of KOH , the ionic strength of the KOH solution would:_____.
A. Increase.
B. Decrease.
C. Not change.
2) If a dilute solution of KOH were added to a solution of CaCl2 (Ca(OH)2 (s) is formed), the ionic strength would:____.
A. Increase.
B. Decrease.
C. Not change.
3) If a dilute solution of benzoic acid were titrated with a solution of KOH the ionic strength would:____.
4) If a solution of NaOH were added to a solution of iron(II) chloride, the ionic strength would:____. A. Increase.
B. Decrease.
C. Not change.

Answer 1

1) increases

2) decrease

3) increase

4) decrease

Step-by-step explanation:

When ionic compounds dissolve in water, the concentration of ions in solution increases since ionic substances dissociate into ions in solution. The greater the concentration of ions in a solution, the greater the ionic strength of that solution.

Hence, if HNO3 is added to KOH solution, the ionic strength of the solution is increased due to an increase in the number of ions in the solution.

Also, when benzoic acid is titrated against KOH, potassium benzoate (an ionic substance) is formed thereby increasing the ionic strength of the solution.

However, when KOH is added to CaCl2, a precipitate (Ca(OH)2) is formed. Also, when NaOH is added to FeCl2, a precipitate (Fe(OH)2) is formed. In both cases, the formation of the precipitate decreases the concentration of ions in the solution thereby decreasing the ionic strength of the solution.