6th edition, 14.119

Moderators: Chem_Mod, Chem_Admin

Hai-Lin Yeh 1J
Posts: 89
Joined: Fri Sep 28, 2018 12:16 am
Been upvoted: 1 time

6th edition, 14.119

Postby Hai-Lin Yeh 1J » Sat Mar 09, 2019 9:52 pm

One stage in the extraction of gold from rocks involves dissolving the metal from the rock with a basic solution of sodium cyanide that has been thoroughly aerated. This stage results in the formation of soluble Au(CN)2- ions. The next stage is to reduce gold to the metal by the addition of zinc dust, forming Zn(CN)42-. Write the balanced equations for the half- reactions and the overall redox equation for both stages.

Can someone explain how to write the half-reactions and the overall redox equation for both stages? I don't understand how they decided which reaction they decided to use for oxidation & reduction.

Chem_Mod
Posts: 19138
Joined: Thu Aug 04, 2011 1:53 pm
Has upvoted: 820 times

Re: 6th edition, 14.119

Postby Chem_Mod » Sun Mar 10, 2019 10:18 pm

In the first stage, Au becomes Au(CN)2 - in the anode and O2 + H2O become OH- in the cathode,
In the second stage, Zn becomes Zn(CN)4 2- in the anode and Au(CN)2- becomes Au in the cathode.


Return to “Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust”

Who is online

Users browsing this forum: No registered users and 1 guest