Here we can say that a molecular equation can be written when given a reactant 1 and react in two. If we take a look at this example question, it says predict whether a chemical reaction occurs and write the balanced molecular equation. All right, so write the molecular equation. We're going to follow the given steps.
So step one says we have to break up reaction one and react in two into their ionic forms. If we look at reactant one, it's composed of lithium and hydroxide. Remember, lithium is in Group 1A, so it's plus one. Hydroxide is a polyatomic ion, so it's -1. Magnesium sulfate magnesiums in Group two way, so it's two plus for its charge. Sulfate is 2 minus. Now if you don't quite remember how I'm coming up with these charges, make sure you go back and take a look at my videos on periodic table and charges and then as well as my polyatomic ions concept videos.
So we've done that first part. Step two, we swamp ionic partners by remembering that opposite charges attract. Apply the rules for combining ions based on the numerical values of their charges. All right, so opposite charges attract. This positive will be attracted to this new negative. This negative will be attracted to this new positive. So they're switching partners now. Remember, if the numbers within the charges are different, they don't cancel out. They're going to crisscross. So the one from here would come here, the two from here would come here. That would give me Li2O4 plus. Then we're going to have the one from here come over here, the two from here come over here, here. That would give me MG. And then the two is for oh wait, so O2, this you can find when we talked about naming ionic compounds and writing ionic compounds.
So again, everything we've learned about ionic compounds up to this point is necessary to effectively write a molecular equation. All right. So we've written out what the products are. Now step three is important. We're going to say a reaction occurs only occurs if a solid gas or liquid water is formed as a product. If both of the products formed are aqueous, meaning they're soluble, then no reaction has occurred and we stop. We just say no reaction. Here we have to use the solubility rules to determine if the product's form will be soluble or insoluble.
So let's come back up here. One product that we made is Lithium Sulfate. Remember Ghana Cash and Cops? Lithium is a group 1A element, so that's part of Ghana, right? So anything connected to a Group One AI is automatically soluble. So this would be aqueous magnesium hydroxide. Hydroxide is part of cops. We say that hydroxides are insoluble unless they're connected to CBS, calcium, barium or sulfur. Also, if they're connected to things from Ghana, Ghana, cache, they could also be soluble. But here hydroxide is not connected to calcium, barium or sulfur, and magnesium is not part of gonocaching anyway. So here this would be solid.
So we just created a solid. So we know a reaction has occurred because remember you have to create a solid gas or liquid water. So Step 4, if necessary balance your molecular equation by placing the correct coefficients in front of each, in front of each molecule. So we're going to do that now. We're going to place the right coefficient in front of each molecule. So coming back U, if we look at our balanced equation or unbalanced equation, we have two lithium's here, but only one here O we're going to put a 2 here. Now we have 2 lithiums, but it also gives us 2 hydroxides. That's OK, because look, we have two hydroxides here. Then what do we see? We see that we have one magnesium, one magnesium, one sulfate, 1 sulfate. So our equation is balanced. So if we write all the coefficients in front it would be 2:1:1 and 1:00. So this would represent our balanced molecular equation.