As part of the analysis of water samples, the hardness of water is commonly measured and calculated. It is commonly expressed in ppm by mass (parts per million) of CaCO3. Parts per million is also equivalent to milligrams of CACO3 per liter of water. In a sample taken by an environmentalist, he was able to observe a hardness count of 205 mg CacO3/L. Given this hardness count of the sample, what is the molar concentration of Ca2+ ions in the water sample?

1. The Ksp of Ca3(PO4)2  is 1.3 × 10−26. Estimate the solubility of this salt in units of g. L−12. If a sample of solid Ca3(PO4)2 is stirred into exactly one litre of a 0.550M solution of Na3PO4, how will the solubility of the salt compare with the answer that you have obtained in question 2.1? Explain you answer in a short sentence.

Consider the graph below that displays the solubility of KCI in water as a function of temperature. 50 g of KCI is mixed with 100 g of water at 25 °C and is then heated to 50 °C. Select which statement best describes what would be observed as the system proceeds to establish equilibrium. 100 Solubility (g per 100 g H₂O) 80 60 40 20 0 20 KCI 40 60 Temperature (°C) 80 100 O a. A homogeneous solution of hydrated ions is initially observed, when a further 10 g of KCI is added, some of the added KCI is observed to dissolve, but some of the additional KCI remains in solid form. O b. A heterogenous system involving an equilibrium between hydrated KCI ions and solid KCI is observed. O c. A homogeneous solution of hydrated ions is initially observed, when a further 1 g of KCI is added, this additional KCI is also observed to dissolve. O d. A homogeneous solution of hydrated ions is observed before spontaneous crystallisation of KCl occurs when the solution is poured onto a crystal of KCI.

Write the general equilibrium constant for 2 NaBr(aq) + Pb(ClO4)2(aq) → PbBr2(s) + 2 NaClO4(aq).  K = 1 / [Pb^2+][Br^−] 2  K = [NaClO4]^2 /  [NaBr]^2 [Pb(ClO4)2] K = [Pb^2+][Br−]^2  K = [PbBr2] / [Pb^2+][Br−]^2  K = 1 / [Pb(ClO4)2][NaBr]^2