Gold metal is extracted from its ore by treating the crushed rock...

Question

Gold metal is extracted from its ore by treating the crushed rock with an aerated cyanide solution. The unbalanced equation for the reaction is  
(a) Balance the equation for this reaction in basic solution.

Accepted Answer

welcome back everyone. One method of obtaining copper is by ammonia leaching, which involves the following reaction. Where solid copper reacts with oxygen gas to produce our tetra amine copper caddy on bounce the reaction equation in basic solution. So our first step is to write out the entire equation into half reactions by separating by our re agents or our reactant. So we begin with our copper solid, which is going to be reacting with ammonia to form our copper or tetra amine copper caddy on. This is our first half reaction. Our second half reaction is going to be our oxygen gas, which is going to form water as a product. Next, we want to recall that we balance non hydrogen and oxygen atoms first. So beginning with looking at our first half reaction, let's focus on balancing our nitrogen. We have foremost on the product side and just one on the reactant side. So we're going to add a coefficient of four in front of ammonia on the reactant side, which will now also give us 12 moles of hydrogen on the react inside to match with the 12 moles of hydrogen on the product side. We can see that our copper atom is balanced and now let's move to our second half reaction where in order to balance out the hydrogen that is missing on the reactant side, we need two moles of that. We're going to recall that we can add hydride as a second reactant so we would add two moles of H plus to bounce out with the hydride on the product side and actually just to make a correction, we need to balance out oxygen first. So we see that we have two moles of oxygen on the reacting side. We're going to place a coefficient of two in front of water, which will actually give us four moles of hydrogen. And so we would add instead four moles of H plus hydride. Now that we have our atoms balanced in both of our half reactions, we now need to balance out the charges in both of our reactions on both sides. So beginning with our first reaction, we have a net charge of plus two on the product side, which we can cancel out to get a net charge of zero by adding two electrons as a product. Next, in our second half reaction we have a net charge of plus four on the reactant side. So we're going to expand our reactant side and add four electrons as a reactant to cancel that charge out. So that we have neutral charges on both sides of our equation. Or just a neutral. Sorry, no charge on both sides of our equation. And so now we need to make sure that we can get an overall reaction by having bounced electrons in both of our half reactions. We have four electrons here in this second reaction. And in the first reaction we have two electrons. So we're going to fix that by taking the entire first equation and multiplying it by two. So this is now going to give us two moles of copper Plus 12 moles of Ammonia. So this is a 12 here Yields two moles of tetra amine copper caddy on Plus four electrons. And now we can add these two reactions together to come up with an overall equation where we'll have our electrons cancel out here on the react inside and here on the product side and everything else we're going to carry down. So we'll have overall two moles of solid copper plus eight moles. And that is why this is actually an error here. This should be eight moles of ammonia since we have four times two. So eight moles of NH three, this produces or actually we still have one more reacting to add, we have to add the one mole of oxygen gas from the second reaction as well as the four moles of hydride from the second reaction. And now we will produce our products where we have two moles of our tetra amine copper cat ion, Plus our second reactant, which is from the second reaction, two moles of water. So now that we have this overall equation, we need to recognize that because we have hydride in the mix. And this is a basic solution, we want to recall that we always react hydride with hydroxide. And so we need to add hydroxide to both sides of our equation. So what we'll have is an equivalent edition of hydroxide being four moles of hydroxide to both moles, or sorry to both sides of our reaction. So we have Two moles of and we'll actually write this out in red. We have two moles of solid copper plus eight moles of NH three plus one mole of oxygen gas, plus four moles of hydride, which we must react. Since this is a basic solution with four moles of hydroxide To produce two moles of tetra amine copper cat ion Plus two moles of water Plus four moles of hydroxide. Since we have to bounce that out on the product side as well. And so now that we have hydroxide added, we are going to recognize that hydroxide and our formals of our hydride are going to combine to form water. So we won't have that happen on the product side, since we actually don't have any hydride caddy on on the product side, we only have that on the reactant side. So we're going to just simplify in our next line so that we have two moles of solid copper plus eight moles of ammonia Plus one mole of oxygen gas plus we'll have two moles of water when we have the combination of formals of hydride and formals of hydroxide, or sorry, four moles of water here and then on our product side we have our arrow. We have two moles still of our tetra amine copper cat ion Plus two moles of water Plus four moles of hydroxide. And now we'll see that we can cancel out the common species just as we did before when we were adding our two reactions where we can get rid of the two moles of water on the product side with one set of the two moles of water on the reactant side, which will leave us with two moles of water here on the reactant side now and this should actually be liquid here as the symbol. So next we'll just simplify to our balanced redox reaction, which is now going to be as a whole two moles of copper solid plus eight moles of ammonia Plus one mole of oxygen gas. Sorry, this is oxygen gas here Plus two moles of water left since we've canceled them out With the two moles on the product side yields two moles of our tetra amine copper caddy on, Plus four moles of hydroxide. And this entire equation is going to be our final answer as our balanced redox reaction in basic solution. I hope everything I explained was clear. If you have any questions, please leave them down below and I'll see everyone in the next practice video

Gold metal is extracted from its ore by treating the crushed rock with an aerated cyanide solution. The unbalanced equation for the reaction is (a) Balance the equation for this reaction in basic solution.

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