Look at the location of elements A, B, C, and D in the following

periodic table:

(c) Which hydrides react with water to give H2 gas? Write a balanced net ionic equation for each reaction.

Video transcript

Hi, everybody. Welcome back. Our next problem says, given the elements Roman numerals 123 and four in the periodic table below, identify the elements with the simplest binary hydride that react with water to produce H two gas and provide a balanced net ionic equation. For each, we're given a periodic table with these four elements and then four answer choices with different net ionic equations. So we're going to break this down in two parts. In part one, let's identify the elements were given, I'm going to label them in red on the periodic table to make them stand out of it. Element number one is in group one, a row five. So this is Rubidium RB, element two is in group two, a row five. So that's strontium sr I let my number three is in group six, a row three. So that's sulfur S an element and number four is in group seven a row two. So that's flooring F. So we need to think about which of these would form a binary hydride that will react with water to produce hydrogen gas. Well, production of hydrogen gas comes from ionic hydride where the hydride ion is H minus H minus is a really good proton acceptor. So it can react with water or with acid to combine with protons to form hydrogen gas. And which type of elements will react with hydrogen to form these ionic hydride or something that will donate electrons to make that H minus ion who donates electrons metals. So we're gonna be looking at the left side group, one A and two A and that will be the rubidium and strontium. Our other two elements, sulfur and fluorine being nonmetals will react to form covalent hyd rides. So that isn't what we're looking for. So we can eliminate any answer choices that involve hydride with sulfur or fluorine, although there are none fluorine but answer choice B and answer choice D the second set of equations involves a reaction with a sulfur hydride. Choice A and choice C involve rubidium and strontium. So we're going to need to choose between them. So first, we need to think about which hydride rubidium and strontium will form. We need to think about the oxidation states of those two. Well, rubidium being group one A will be in a plus one oxidation state. So its high drive will be RBH. And we see that choice A and choice C both show RBH ionic hydride are in the solid state. As our equation shows we need to look at strontium. It's in group two A, it will have a plus two oxidation state So its hydride will be srh two, you'll need two hydrogen atoms to react. So that actually eliminates choice a because choice A has strontium combining with just one hydrogen. So just by the process of elimination, we have reached our answer of choice. C which correctly has srh two in a solid state. But to be thorough, let's just walk our way through this reaction to make sure it's correct and understand how it happens. We have both, both hydrates, reacting with liquid water. Strontium hydride has to react with two molecules of water. Because of the two hydrogens, we know that our water will donate a proton to form the hydrogen gas. But it will also of course, produce Noh minus hydroxide ion that is going to react with our metal. So with rubidium with its plus one state, we'll produce RBOH with strontium sr and then oh in parentheses, two, if we look at our solubility rules group, one, a hydroxides are soluble. So RBOH will be aqueous and the hydroxides of calcium barium and strontium and group two A are also soluble. So both of these hydroxides will be aqueous since they are. And we need to write a net ionic equation. We need to break them down into their ions. And we see that indeed, when we look at answer choice c, our rubidium hydride plus water forms hydrogen H two gas as we were informed and then one RB plus aqueous and +10 minus aqueous. Our strontium hydride reacts with liquid water to form two molecules of hydrogen, two gas since we had two hydrogen atoms in our original compound, one sr two plus ion aqueous and 20 minus ions aqueous as well. So we have our net ionic equation and we've identified the elements that will react, that form a hydride that will react with water to form hydrogen gas. So that's choice C rubidium hydride plus water making hydrogen gas H two plus RB plus plus oh minus and then strontium hydride, srh two plus two molecules of water leading to two molecules of H two gas and sr two plus ion and 20 minus ions. See you in the next video.