The discovery of hafnium, element number 72, provided a controversial episode in chemistry. G. Urbain, a French chemist, claimed in 1911 to have isolated an element number 72 from a sample of rare earth (elements 58–71) compounds. However, Niels Bohr believed that hafnium was more likely to be found along with zirconium than with the rare earths. D. Coster and G. von Hevesy, working in Bohr's laboratory in Copenhagen, showed in 1922 that element 72 was present in a sample of Norwegian zircon, an ore of zirconium. (The name hafnium comes from the Latin name for Copenhagen, Hafnia). (c) Solid zirconium dioxide, ZrO2, reacts with chlorine gas in the presence of carbon. The products of the reaction are ZrCl4 and two gases, CO2 and CO in the ratio 1:2. Write a balanced chemical equation for the reaction.

Video transcript

Hi everyone for this problem, we're told that ozone reacts with hydrogen sulfide to form oxygen gas and sulfur balance this redox reaction in acidic condition. Okay, so when it comes to something being an acidic condition with redox reactions, it means we're adding hydrogen or water in order to balance it. So let's start off by writing our half reactions. So we have ozone is going to form oxygen gas and we have hydrogen sulfide is going to form sulfur. Okay, so now that we wrote out both of our half reactions, what we're going to do first is balance our atoms. We need to make sure our atoms are balanced. So looking at our first half reaction, we have three oxygen's on one side and two on the other. So here we can add a water molecule to the right side to balance out that oxygen. Okay, so now after we've added this water molecule, you can see we have three oxygen's on the right side and three oxygen on the left side. But by adding water we added two hydrogen to the right side. So that means we need to add to hydrogen to the left side. Okay, And for the second half reaction, to make sure that atoms are balanced, we have one sulfur on the left side and one sulfur on the right side. So those are balanced but on the left side we have two hydrogen. So that means we need to add two hydrogen on the right side. Okay, so now our atoms are balanced. The second thing that we need to do is confirm that the total charge matches on both sides. And so for our first half reaction, let's see what our charge is. We have a two H plus. So that means we have a positive two on the left side. And we can say that charge is equal to our charge on the right. So on the left side we only have a plus to charge. The ozone doesn't have a charge On the right. So our total charge on the left is positive to our total charge on the right is zero because our 02 gas does not have a charge and neither does our water. Now we need to make sure our charges match on both sides. So on the left we have positive two on the right, we have zero. So we need to add two electrons to the side with the higher charge. Okay, so we're going to add two electrons to the left side by adding two electrons to the left side. Now we're going to have a zero charge on the left side and now our charges are going to equal each other. So this is going to cancel out. Okay, so now our charges balance on both sides. For the first half reaction. Let's take a look at the second half reaction to balance our charges. So on the left side We have a total charge of zero is equal to on the right side, we have a total charge of positive two. Okay, so we need these charges to match. So we're going to add two electrons to the right side because by doing so that's going to make the right side zero. So now our charges are balanced. Okay, The next thing that we need to do is make sure that our number of electrons equal each other for both of our reactions. Both of our half reactions. And they do for the first half reaction, we have two electrons and the second half reaction, we have two electrons. So that's good. If they didn't match, we would have to make the match by multiplying both of them by a number that would make them equal to each other. But in this case we don't have to do that. Okay, so now we can cancel out whatever we see now, we can cancel out what reappears on both sides. Okay, so we have two electrons canceling out. They have to appear on both sides of the equation in order to cancel. And then we have two hydrogen that cancel each other. Now we add up both of our half reactions and it's going to give us our balanced redox reaction. So now we're going to add everything on the left side together for both of our half reactions and do the same for the right side. So we get for the left side, ozone gas plus hydrogen sulfide is equal to oxygen gas plus water plus sulfur. Okay, and this is our final balanced redox reaction. That's the end of this problem. I hope this was helpful.