Question

Calculate the concentration of Tl+ when TlCl just begins to precipitate from a solution that is 0.0250M in Cl−.

a) 1.25×10−2M
b) 2.50×10−2M
c) 5.00×10−3M
d) 1.00×10−3M

Answer 1

The concentration of Tl+ when TlCl starts to precipitate from a solution that is 0.0250M in Cl- is determined using the Ksp of TlCl and the given Cl- concentration. The calculated concentration of Tl+ approximates to 5.80 × 10−3 M, which is closest to the provided option c) 5.00 × 10−3 M.

Step-by-step explanation:

To calculate the concentration of Tl+ when TlCl begins to precipitate, we use the solubility product constant (Ksp) of TlCl. The Ksp can be determined from the equilibrium concentration of ions in a saturated solution given by [Tl+] = 1.21 × 10−2 M and [Cl−] = 1.2 × 10−2 M, thus Ksp = [Tl+][Cl−] = (1.21 × 10−2 M)(1.2 × 10−2 M) = 1.45 × 10−4.

Now, given a solution that is 0.0250M in Cl−, we can find the concentration of Tl+ needed to start precipitation by rearranging the Ksp expression: [Tl+] = Ksp / [Cl−] = (1.45 × 10−4) / (0.0250 M) = 5.80 × 10−3 M, which is closest to option c) 5.00 × 10−3 M.