(a) Using the ion-pair equilibrium constant from Appendix J, with activity coefficients 1, find the concentrations of species in 0.025 M MgSO4. Hydrolysis of the cation and anion near neutral pH is negligible. Only consider ion-pair formation. You can solve this problem exactly with a quadratic equation. Alternatively, if you use Solver, set Precision to 1e-6 (not 1e-16) in the Solver Options. If Precision is much smaller, Solver does not find a satisfactory solution. The success of Solver in this problem depends on how close your initial guess is to the correct answer. (b) Compute a new ionic strength and repeat part (a) with new activity coefficients from the Davies equation. Perform several iterations until the ionic strength is constant. The fraction of ion pairing that you find should be close to that in Box 7-1, which was derived with Debye-Hckel activity coefficients. (c) We naively assigned the ionic strength of 0.025 M MgSO4 to be 0.10 M. What is the actual ionic strength of this solution? 1

Chapter Four Relevant Periodic Groups 1) Group 1A = Alkali Metals *they have a charge of 1+ 2) Group 2A = Alkaline Earth Metals *they have a charge of 2+ 3) Group 7A = Halogens * they have a charge of 1 4) Group 8A= Noble Gases * they are neutral. They don’t bond with anything. Elements are formed by nuclear reactions in stars at high temperatures. Rules for Orbital Filling 1) Pauli Exclusion Principle → No two electrons have same four quantum number. 2) Hund’s Rule → Electrons will pair only if there is no orbital of exactly the same energy available 3) Aufbau Principle → Electrons fill in this order ; 1s,2s,2p,3s,3p….etc EXCEPTIONS 1s,2s,3s,3p,4s,3d,