- M1b1 2018 7 Question 4 An Ore Sample Collected Near The Orange River Was Treated So That The Resulting 25 0 Dm Soluti 1 (196.21 KiB) Viewed 29 times
M1B1 2018 -7- QUESTION 4 An ore sample collected near the Orange river was treated so that the resulting 25.0 dm³ solution contained 0.00226 mol dm-3 of Ni²+ (aq) ions and 0.00125 mol dm-3 of Co2+ (aq) ions. The solution was kept saturated with an aqueous solution of 0.0250 mol dm-3 H₂S. The pH was then carefully adjusted to selectively precipitate the first metal ion (as a metal sulphide) from the second. The first precipitate was filtered off from the remaining solution, dried and reduced to its pure metal form. The pH of the remaining solution was then carefully adjusted for the second time until the entire concentration of the second metal ion, together with a trace concentration of the first metal ion, were co-precipitated as metal sulphides. This co-precipitate was also filtered off, dried and reduced to the metal form. Based upon this information and that in the data sheet, calculate: 4.1 The pH at which maximum separation of the two metal ions was achieved. 4.2 The percentage mass impurity of the metal that was obtained from the reduction of the last precipitate. (12) (8) [20] QUESTION 5 5.1 Distinguish between the terms "salt bridge" and "liquid junction". 5.3 Calculate the cell potential of the following cell at 25.0°C: Cu Cu(CN) (0.224 mol.dm-³) CN- (0.122 mol.dm-³) cul || H* (pH of 4.68) H₂ (1.00 atm) (Pt) (10) [14] 4.1 42