You could use potassium iodide or sodium iodide. So you add a source of iodide anions, and that makes this reaction fast. So your iodide anion is your catalyst; it increases the rate of a reaction. Let's take a look at the mechanism for the reaction when we add our iodide anion as our catalyst.
So in the first step of the mechanism, you can see we have H2O2 and our iodide catalyst, and this forms the hypoiodite ions. So this is our intermediate, so the hypoiodite anion is our intermediate and we also are given the information that this first step of the mechanism is the slow step.
And the second step of the mechanism, alright we have another molecule of hydrogen peroxide reacts with our intermediate, our hypoiodite ion and we get our oxygen, and this step is fast. Remember, for a mechanism, a possible mechanism must have elementary steps that add up to the overall reaction. So if we add our two steps together, we should get our overall reaction. So we're gonna add all of our reactants together, so that would be H2O2 plus I- plus another H2O2 plus IO- and that should give us our products.
So we have a lot going on there. Let's see what we can cancel out. So what do we have on both sides? Well we can cancel out the iodide, that's on the left and that's on the right. That's our catalyst. It increases the rate of the reaction but it's not consumed. You can see we're using it in the first step, but the iodide anion is regenerated in the second step.
So overall, our catalyst is not consumed. And then we have our intermediate. The hypoiodite ion is on the left side and on the right side, so we can cancel that out. Our intermediate is created in the first step, but then it's consumed in the second step. So what are we left with here? The fuel cell needs to separate the atoms in molecules of hydrogen and oxygen so that those atoms can reshuffle to create new molecules water. Without some assistance, though, that reshuffling would take place very slowly.
So the fuel cell uses a catalyst — platinum — to propel those reactions along. Platinum works well in fuel cells because it interacts just the right amount with each starting gas. In effect, it pulls them close together so that it encourages — speeds along — their reaction. Then it lets its handiwork float free. For years, other technologies have relied on platinum catalysts, too. To remove harmful pollutants from exhaust gases, for instance, cars now rely on catalytic converters.
But platinum has some downsides. People like to use it in fancy jewelry. Some other catalysts have risen to superstar status. Among them are palladium and iridium. Like platinum, however, both are expensive and hard to get. Some scientists think that carbon molecules might work. They certainly would be less costly and readily abundant. A catalyst is a substance that:. Only a very small mass of catalyst is needed to increase the rate of a reaction.
However, not all reactions have suitable catalysts. Catalysts only affect the rate of reaction - they do not affect the yield of the reaction. A catalysed reaction produces the same amount of product as an uncatalysed reaction but it produces the product at a faster rate. Different substances catalyse different reactions. The table describes three common catalysts. Notice that these catalysts are transition metals or compounds of transition metals. A catalyst provides an alternative reaction pathway that has a lower activation energy than the uncatalysed reaction.
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