Applying Concepts These questions test conceptual learning. Gold can be dissolved from...

Applying Concepts

These questions test conceptual learning.

Gold can be dissolved from gold-bearing rock by treating the rock with sodium cyanide in the presence of the oxygen in air.

Once the gold is in solution in the form of the [Au(CN)₂]^-ion, it can be precipitated as the metal according to this unbalanced equation:

(a) Are the two reactions above acid-base or oxidationreduction reactions? Briefly describe your reasoning.

(b) How many liters of 0.075-M NaCN will you need to extract the gold from 1000 kg of rock if the rock is 0.019% gold?

(c) How many kilograms of metallic zinc will you need to recover the gold from the [Au(CN)₂]^- obtained from the gold in the rock?

(d) If the gold is recovered completely from the rock and the metal is made into a cylindrical rod 15.0 cm long, what is the diameter of the rod? (The density of gold is 19.3 g/cm³.)