Experiment 7: Solubility, Equilibrium and Thermodynamics - Solubility of Calcium Hydroxide

What is the purpose of the experiment involving calcium hydroxide (Ca(OH)₂)?

To investigate how temperature affects the solubility of Ca(OH)₂ and to determine its thermodynamic properties by measuring the solubility product (Ksp) at different temperatures.

What is the dissolution reaction of Ca(OH)₂?

Ca(OH)₂ (s) ⇌ Ca²⁺ (aq) + 2 OH⁻ (aq)

What does Ksp represent in the context of saturated solutions?

Ksp is the solubility product, expressed as Ksp = [Ca²⁺][OH⁻]².

How is ΔG° related to Ksp according to thermodynamics?

ΔG° = -RT ln Ksp.

What thermodynamic equation describes the relationship between ΔG°, ΔH°, and ΔS°?

ΔG° = ΔH° - TΔS°.

What does a plot of ΔG° vs. T yield in terms of thermodynamic properties?

The slope equals -ΔS° and the y-intercept equals ΔH°.

What is the expected behavior of solubility with temperature if the dissolution is endothermic?

Increasing temperature increases solubility.

What should be done to prepare saturated solutions of Ca(OH)₂?

Dissolve ~0.5 g of Ca(OH)₂ in 50 mL DI water at three temperatures: ice bath, room temp, and boiling.

What indicator is used during the titration of Ca(OH)₂ with HCl?

Bromothymol blue.

How can ΔG° and Ksp be calculated at 25°C?

Use the derived values from the LINEST analysis of ΔG° vs. T graph.