Aluminum sulfide reacts with water to form aluminum
hydroxide and...

Question

Aluminum sulfide reacts with water to form aluminum
hydroxide and hydrogen sulfide. (a) Write the balanced
chemical equation for this reaction. (b) How many grams of 
aluminum hydroxide are obtained from 14.2 g of aluminum 
sulfide?

Accepted Answer

Alright. So in this practice problem, we need to write a balanced reaction for the reaction of aluminum sulfide with water and it's going to be producing aluminum hydroxide and hydrogen sulfide in addition to that, we have some study geometry. So, if we have 10.5 g of aluminum sulfide that was allowed to react. We need to calculate the massive aluminum hydroxide produced. All right. So, we need to basically turn these chemical names into chemical formulas and then write the balanced equation and then do some study geometry. Okay, so aluminum sulfide. So aluminum we know has a positive three charge. Right? It's a group 38 and self sulfide is just sulfur and it has a negative two charge because it's in Group 68. So aluminum sulfide, whenever we combine these together, the charges will come will exchange. And we're going to have aluminum two and then a sulfur three. So this is aluminum sulfide. Okay, it is reacting with just water and we know water is just H 20. Okay, and it's going to be producing producing aluminum hydroxide. So again, aluminum is aluminum plus three. And hydroxide, iron is just oh h minus. Right, so here, in order to combine these together, we're actually going to need three hydroxide is in order to combine into a neutral compound. So we're going to produce produce A L. And then ohh three. So this is aluminum hydroxide and then hydrogen sulfide. So hydrogen is just hydra generated H plus and sulfide. Again, it's just a sulfur but it has a negative two charge. So we need to hydrogen in order to combine with one sulfur. So we're going to have a church too. Yes. Okay, so that's hydrogen sulfide. So now that we have a chemical reaction or equation, we need to balance it now. Okay, so let's go ahead and do that. Alright, so we have to aluminum, we're going to put two here. We have. Let's see for the hydrogen. We have 678. So we have eight in total, but our sulfur are not balanced. So we need three in front of H two S to balance the three sulfur. So now we have actually um six 12, 12 oxygen's. So we need a six here. Six times two is 12. Alright, so now it's balanced. Let's go ahead and go back here and do some stock geometry. So we have we're told that we have 10.5 g of aluminum sulfide, which is this reactant here. Right, so we have 10 .5 g of aluminum sulfide and we need to figure out how many masks. So in grams of aluminum hydroxide. So this guy, how much of this guy do we have that's produced? Okay, so now first we're going to convert these grams of aluminum sulfide into moles to do that. We need the molar mass of aluminum sulfide. So in one mole. How many grams do we have? Let's go ahead and figure out. So we have aluminum, We have two of them. If you take a look at the periodic table, aluminum weighs 27 g. And then we have sulfur. We have three cell furs and it weighs 32. g each. So this will give us 54 for aluminum and 96.18 for Sulfur. Okay, so let's go ahead and add that together. This is supposed to be an eight. There we go. So add that together and that should give you 150. grams per mole. So that's the molar mass of aluminum sulfide. And we're going to plug that in here, grams of aluminum sulfate. Alright, so now we can cancel out the grams. And now we have moles now that we have moles, we are going to be using our balanced equation to do a multiple comparison. Now, what do we want? We want information on aluminum hydroxide. Right, so we need to get aluminum hydroxide and cancel aluminum sulfide. So we can see that we are using only one mole. Right? So there's just one more here of aluminum sulfide. So we're gonna put that on the bottom. So for every one mole of aluminum self sulfide, we produce two moles of aluminum hydroxide. So two moles of a L. Ohh there you go on the top. So now we can cancel out the moles of aluminum sulfide. And now we're going to have moles of aluminum hydroxide. Now we don't want moles. We do want mass and grams. Right, so let's go ahead and convert that into grams. So one more of a L O H Oh, age three, how many grams are there? I'm gonna go ahead and find the molar mass of that down here. So aluminum, oxygen and hydrogen. Okay, so again, just one aluminum here it is 27 g for the oxygen. There are three of them Times 16. Um that will give us 48 grams. And then for the hydrogen there are three of them And they weigh 1.01 each. There we go. So altogether that will weigh 78. g per mole. Alright, so that's the molar mass. So in one mole there are 78.03 g of aluminum hydroxide. It gets really old. Right? Having to like rewrite all of these formulas um in your calculations, but if you do it is easy to keep track of what's what? Right? Because if you have a lot of stuff going on, you might forget what exactly you're working with. Alright, so notice that everything here is canceled. And our answer which I'm going to put on the bottom over here Is going to be in grams of aluminum hydroxide. Right? So let's go ahead and divide and multiply everything correctly here and we should get 10.9 grams of aluminum hydroxide. Alright, so here's our final answer. There we are. We can go ahead and round it up to 11 g if we want, since it's 10.9 can round that up. But we are all done. If you have any questions, let us know and we'll see you in the next video.

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