Tooth enamel is made up of hydroxyapatite, Ca_10(PO_4)_6(OH)_2 or the empirical formula, Ca_5(PO_4)_3(OH). Use the empirical formula for all calculations because stoichiometry plays two significant roles.
A. Print the balanced chemical equation for the molar solubility of hydroxyapatite in pure water. An appropriate arrow is expected.
B. Print the Ksp mass action or solubility product equilibrium concentration constant for the molar solubility of the insoluble solid in pure water.
C. Calculate the molar solubility of tooth enamel in pure water if the Ksp is 6.8X10^-37.
D. Recalculate the molar solubility in a 0.005 M calcium nitrate solution.
I would do this and found evidence on the web that the ionization products are as follows:
Ca5(PO4)3(OH) ==>5Ca^+2 + 3PO4^-3 + OH^-
Ksp = (Ca^+2)^5*(PO4^-3)^3*(OH)
C. Set up an ICE chart and substitute into the Ksp expression.
D. Do the same as C but substitute 0.005 for (Ca^+2).
Post your work if you get stuck.
A. To write the balanced chemical equation for the molar solubility of hydroxyapatite in pure water, we need to understand the dissociation of hydroxyapatite in water.
The empirical formula for hydroxyapatite is Ca5(PO4)3(OH). When it dissolves in water, it dissociates into its constituent ions.
The balanced chemical equation for the molar solubility of hydroxyapatite in pure water can be written as:
Ca5(PO4)3(OH) ⇌ 5Ca2+ + 3PO43- + OH-
B. The Ksp (solubility product constant) is an equilibrium constant that relates to the solubility of an insoluble solid in a solution. For hydroxyapatite, the solubility product constant can be expressed as:
Ksp = [Ca2+]^5 * [PO43-]^3 * [OH-]
C. To calculate the molar solubility of tooth enamel in pure water, we can use the solubility product constant (Ksp) value provided.
Given:
Ksp = 6.8 x 10^-37
Since the Ksp value represents the product of the concentrations of the constituent ions at equilibrium, we can set up the following equation:
Ksp = [Ca2+]^5 * [PO43-]^3 * [OH-]
We need to solve for [Ca2+], which represents the molar solubility of tooth enamel.
D. To recalculate the molar solubility in a 0.005 M calcium nitrate solution, we need to consider the effect of the presence of calcium ions.
Since calcium nitrate is a strong electrolyte, it dissociates completely in water, providing calcium ions (Ca2+). This changes the concentration of calcium ions in the solution.
To recalculate the molar solubility, you would need to take into account the additional calcium ions from the calcium nitrate solution. The new concentration of calcium ions ([Ca2+]) would be the sum of the concentration of calcium ions from the calcium nitrate solution (0.005 M) and the concentration originated from the dissolving hydroxyapatite.
By substituting this new concentration of [Ca2+] into the solubility product expression, you can calculate the new molar solubility in the calcium nitrate solution.