97. What weight of metallic copper will be deposited from a cupric salt solution by a current of 1.5 amperes during a period of 45 minutes, assuming 100% current efficiency? (1 Faraday = 96,500 coulombs.)
!Answer!: 1.335 grams.
98. In the electrolysis of a 0.8000 gram sample of brass, there is obtained 0.0030 gram of PbO_{2}, and a deposit of metallic copper exactly equal in weight to the ignited precipitate of Zn_{2}P_{2}O_{7} subsequently obtained from the solution. What is the percentage composition of the brass?
!Answers!: 69.75% Cu; 29.92% Zn; 0.33% Pb.
99. A sample of brass (68.90% Cu; 1.10% Pb and 30.00% Zn) weighing 0.9400 gram is dissolved in nitric acid. The lead is determined by weighing as PbSO_{4}, the copper by electrolysis and the zinc by precipitation with (NH_{4}){2}HPO{4} in a neutral solution.
(a) Calculate the cubic centimeters of nitric acid (sp. gr. 1.42 containing 69.90% HNO_{3} by weight) required to just dissolve the brass, assuming reduction to NO.
!Answer!: 2.48 cc.
(b) Calculate the cubic centimeters of sulphuric acid (sp. gr. 1.84 containing 94% H_{2}SO_{4} by weight) to displace the nitric acid.
!Answer!: 0.83 cc.
(c) Calculate the weight of PbSO_{4}.