Question

The MacArthur-Forrest process is a metallurgical technique for extracting gold from low-grade ore by converting the gold to water soluble aurocyanide metallic complex ions. It is the most commonly used process for gold extraction. Subsequent processing of aurocyanide allows recovery of pure gold. 4 Au 8 NaCN 02 2 H2O 4 NaAu(CN) 2 + 4 NaOH 1) Using 150,000.0 Liters of 0.0025 M NaCN [sodium cyanide; MW-49.0 g/mol], what theoretical weight in kilograms of gold metal [Atomic Weight 197.0 g/mol] might be obtained following the reprocessing of the NaAu(CN) 2 formed? [7 points] Potassium hydroxide (KOH) is a strong base. For a solution that is 0.450 M, determine the following: 2) [3 points] Its hydrogen ion concentration Its pH Its pOH

Answer 1

Aus-1 Cinen- + 4 Na Au (CN)2 t u Nadu 4 Auta NOCN + 0 + 2H₂O Mac-Arthur process 150,000.0 litres of 0.8025M NOCN (MW=49 glueel) to find weight in kilograme of gold metal 4 Aut & Na CN + O₂ + 2H₂0 - 375 NACN+04+24,0 - 4 Na Au (CN), +4 N904 375 mole moles of NGEN = 150,660 X 0.0025 = 375 moles Repne te 1870s of Gold GNGAL (CN), + 220 -21a[Zn (CA),] + 444 375 mole weight of goed fermed 5x1979 • 36937.59 weight I goed (in kg): 36.94 kg Thes, using stained Thus, using 150,0000 lither govors M NOCN, we 36.94 kg of gold. K+ +02 Aus 2 Initially finally KOM o.us . 0.45m 0.45m (strong base) pous-log(on] = -log Co.45] pon = 0.347 [M+] x [on'] = 10-14 pHapon = 14 PH: 14 -0.347 el dese [HT] = 13.653 107" : 2.22 71014 0.347 its pH 13.653 Its hydrogen conch. 2:22xvot long h Therefore, Its pon 0.347