Let's take a look at how we can predict the products of a type of reaction, specifically ionic double replacement reactions. So in an ionic double replacement reaction, you have two ionic compounds that are going to switch ions. Remember, in an ionic compound, you have a positively charged cation with a negatively charged anion. These two can share or can exchange partners with a different. ionic compound so that the partners will essentially switch which one has which cation with which anion.
This will make more sense when we go through some examples. We're going to go through a few steps for these. We'll write our ions for the reactants, we'll recombine the ions, determine their solubility so we can see if they actually react. because these types of reactions we're looking specifically for precipitation. So we're looking for a precipitate.
So that's a solid has to be formed. So we need to know whether something is soluble or not to know whether it dissolves in water or whether it will form a solid and fall out of its solution. Finally we'll look at balancing the equation.
Now to be able to do these you already know how to find them. ions from the names or formulas of an ionic compound, but we also need to know solubility. So we need to look at some solubility rules.
So if we look at table 6.1 from your book, it's about predicting if a product is soluble, and we can determine if it's going to be soluble or not based on the type of ions that it contains. This provides us with patterns of what we should be able to predict. If we have a soluble ionic compound, so that means that these are going to form aq, so they're going to be aqueous, they're going to dissolve in water.
Insoluble ionic compounds are going to tend to be borne solids. So the big one here for ones that are soluble or anything that involves a group one cation. So anything with sodium in it, anything with lithium, potassium, these things are going to be always soluble. So if you have a compound that is sodium something, you know it's soluble. You don't have to worry about what the negative ion is that it's with.
It's always going to be soluble in water. If we look at chloride, bromide, or iodide, these are all going to be soluble unless it's with silver, mercury, or lead. Kind of get the idea of how this works. Same with the fluorides, except with group 2 metal cations, so group 2A, lead 2, and iron 3. If we look at our acetate, our bicarbonate, our nitrate, and our chlorate, these are always soluble.
So if you see that in your compound, then you know that it's soluble. That's why it's so important to identify what our ions are. And sulfates tend to be soluble, except for this kind of significant list of exceptions.
The insoluble compounds are kind of the reverse of that. Carbonates, chromates, phosphates, sulfides. These are insoluble, so they'll form solids unless it's with that group 1 cations.
So remember, there's no exceptions to those, so that makes sense. And ammonium. Hydroxides also tend to be insoluble, so don't dissolve in water, they form solids. Unless you have those group 1 cations, remember there's no exceptions there, and barium. So it gives us some ideas.
So you want to make sure that you have this, not just have this table available, but you know how to use it and interpret it. So let's take a look at an example. Let's take a look at predicting the reaction and what the products of the reaction would be for sodium carbonate with iron 3 sulfate. So first we need to identify what our reactants are and what the formula are for.
So sodium, we know sodium is Na plus carbonate, CO3. 2 minus iron, 3 Fe. three plus and sulfate so four two minus so the original formula of our compounds is sodium with carbonate so there's a positive one with a negative two the lowest common multiple of those is two so i'm going to need two sodiums my carbonate if we look remember from our solubility Sodium compounds are aqueous, so that's going to be dissolved in water. Iron, 3, and sulfate. The lowest common multiple between 3 and 2 is 6, so I'm going to need 2 irons, and I'm going to need 3 sulfates.
Notice I put the parentheses around it. to make sure that it's clear that I'm using three of this whole ion. If I look back at my solubility rules, there's nothing in these rules about iron-3, but I do see a rule here about sulfate. Sulfate, and there's no exception for iron-3, so this is going to be a soluble ionic compound. So I know that iron-3 sulfate is going to be aqueous.
So that's my reactants. Now I want to figure out what my products will be in this reaction. Now these are starting with sodium with carbonate, iron 3 with sulfate. So all I'm going to do is I'm going to switch. So iron 3 is going to combine with the carbonate, and sodium is going to combine with the sulfate.
So they're just trading which positive and which negative is together. So let's look at what our products would be. So sodium with sulfate, that's going to be the lowest common multiple is 2. So I'm going to have Na2.
Now I don't need my parentheses because I'm only going to have one sulfate here. So 4. We'll worry about the solubility in just a moment. Then we have Fe2.
three so iron three with carbonate lowest common multiple six again so we have fe2 co3 3. now sodium group 1a so it's always going to be aqueous iron 3 carbonate hmm Let's take a look at our solubility rules again. If I look at my carbonates, notice it's under the insoluble, so it's going to form a solid unless it's a group 1 cation or ammonium. Iron's not a group 1 cation, and it's definitely not ammonium. So our compound is going to be insoluble, so that means it's going to form a solid.
This forms a solid. that means that this reaction does occur. I form a precipitate, so you really want to make sure that you're forming a solid here. If everything stays aqueous, there's no reaction occurring because there's nothing changing. So now that I know what the products will be, I just have to balance my equation.
I have three sulfates here on the left side of the equation. one sulfate here, so I'm going to put sulfate here. So now I'm going to have three, six sodiums, put a three here, so I have six sodiums, three carbonates, three carbonates, two iron threes, two iron threes.
So always make sure that you're balanced. Do make sure and practice creating these equations because it does take a little bit of practice. practice.