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?

Video transcript

Welcome back everyone. To another video, magnesium sulfide reacts with water to form magnesium hydroxide and hydrogen sulfide. We're given two parts in this problem. A states write the balanced chemical equation for this reaction. And B how many grams of magnesium hydroxide are obtained from 11.5 g of magnesium sulfide. Therefore answer choices. ABC and D they give us different balanced equations and different answers for the mass of magnesium hydroxide. Let's begin this problem by writing the equation. It states that magnesium sulfide, this is our first reactant which is MGS because the charge of magnesium is two plus and the charge of sulfide is too negative. We're adding water which is h2o as we know and we are forming magnesium hydroxide. Magnesium has a two plus charge hydroxide has a negative charge. So we need two units of hydroxide, hydro sulfide H two S because the ox station state of sulfur is too negative. Hygen has a positive ox station state. Now we want to balance it out. We have magnesium on each side, one unit that's fine, one sulfur on each side. That's fine. What about hydrogens? Well, we have four of them on the right and two on the left. So we need to add a coefficient of two on the left, which also balances out the two oxygens on the right. So we have our balanced equation and I, we simply want to convert 11.5 g of magnesium sulfide into grams of magnesium hydroxide. So first of all, what we want to do is take 11.5 g of magnesium sulfide convert that into modes. That's always our first step. So what we know is that one mole of magnesium sulfide corresponds to 56.38 grams. So that's the molar mass of magnesium sulfide. This is how we get most of magnesium hydroxide. The reason why they are also most of magnesium hydroxide is because we have 1 to 1 ratio. So we can clearly show that in our calculation, not only by looking at the equation, we can essentially say that if we got most of magnesium sulfide, then we want to cancel them out. And we want to get the most of magnesium hydroxide according to the balanced equation, it's a 1 to 1 ratio. That's why we are including one and one. So we got the number of modes of magnesium hydroxide. And now we want to use its smaller mass to get grams. So what we're going to do here is simply use the Mueller mass. So we used gram and soap of magnesium hydroxide on the bottom. We're going to use moles of magnesium hydroxide. We know that according to the periodic table, one mole of the substance has a mass of 58.32 g. That's the molar mass. And we can clearly check and see that our units cancel out and we end up with grams of magnesium hydroxide. For complete clarity. We can include MGS for our second conversion factor. And now if we perform the calculations, we get 11.9 grams of magnesium hydroxide. So now let's see which one is the correct option. Well, essentially we can say that option D is the correct answer. D states that the balanced equation is MGS plus two H two equals mgoh two times plus H two S. And for part B, 11.9 grams of magnesium hydroxide are formed. That would be it for today. And thank you for watching.