What pb2+ concentration should be maintained in PbNO3 to produce a solubility of 1.7×10−4 PbI2/L when PbI2 is added?
I found the ksp of PbI2 to be 7.1*10(-9), divided the ksp by the solubility, and took the square root, resulting in 6.5*10(-3). my answer is wrong :s wheres my mistake? :P
nevermind got it. i was using the solubility for pb when it was for i :P
I would look at it this way.
PbI2 ==> Pb^2+ + 2I^-
1.7E-4....x......2*1.7E-4
7.1E-9 = (Pb^2+)(3.4E-4)^2
Solve for (Pb^2+).
0.0614M? which rounds to 0.061 to two s.f.
Your approach is correct, but your mistake lies in the calculation of the square root.
To find the concentration of Pb2+ ions in PbNO3 needed to produce a solubility of 1.7×10^-4 PbI2/L, you can use the equation:
Ksp = [Pb2+][I^-]^2
Given that the Ksp of PbI2 is 7.1×10^-9, and the solubility is 1.7×10^-4 PbI2/L, you can substitute these values into the equation:
7.1×10^-9 = [Pb2+][(1.7×10^-4)^2]
Simplifying the equation:
[Pb2+] = 7.1×10^-9 / (1.7×10^-4)^2
Calculating this expression will give you the correct concentration of Pb2+ ions in PbNO3. Make sure to double-check your calculation to ensure the accuracy of the result.
To determine the concentration of Pb2+ in Pb(NO3)2 that will result in a solubility of 1.7×10−4 PbI2/L, you need to consider the following equation:
PbI2 ⇌ Pb2+ + 2I-
The solubility product constant (Ksp) for PbI2 is given as 7.1×10−9. The expression for Ksp is:
Ksp = [Pb2+][I-]²
Since you have the solubility of PbI2 (1.7×10−4 PbI2/L), you can substitute this value into the expression for Ksp:
Ksp = (1.7×10−4)([Pb2+])([I-]²)
Rearranging the equation to solve for [Pb2+], we have:
[Pb2+] = Ksp / ([I-]²)
Substituting the given Ksp value (7.1×10−9), we have:
[Pb2+] = (7.1×10−9) / ([I-]²)
However, we don't have the concentration of iodide ions ([I-]) in this question. Therefore, you cannot directly calculate the value of [Pb2+].
This means that the approach you initially took by dividing Ksp by the solubility and taking the square root was incorrect. The solubility of PbI2 is only related to the concentration of Pb2+ ions through the Ksp expression.
To accurately determine the concentration of Pb2+ ions in Pb(NO3)2 that will yield a specific solubility of PbI2, you need additional information about the concentration of I- ions in the solution.