In this example problem, we'll look at how to use dimensional analysis to convert from ions to the mass of a compound. The problem states, "What is the mass, in grams, of 3.50 x 10^22 ions of potassium sulfate?" We can start the dimensional analysis using the information we're given in the problem. 3.50 x 10^22 ions. First, we'll want to convert out of ions into moles of ions. We can do this using Avogadro's number. One mole of ions is 6.022 x 10^23 ions. Next, we can convert from moles of ions to moles of potassium sulfate. One mole of potassium sulfate contains two moles of potassium ions and one mole of sulfate ions, so one mole of potassium sulfate is a total of three moles of ions. We use this as a conversion factor to get out of moles of ions and into moles of potassium sulfate. Next, we'll want to convert from moles of potassium sulfate into grams of potassium sulfate. We do this using the molar mass. To calculate the molar mass of potassium sulfate, we need to add together the atomic masses of two moles of potassium, one mole of sulfur, and four moles of oxygen. If we put this in our calculator, we'll get 174.26 grams per mole. We can use this as a conversion factor, where moles of potassium sulfate are on the bottom and 174.26 grams of potassium sulfate are on top. Now, our units should cancel so that we end up with grams of potassium sulfate. If you put this into your calculator, you should get 3.38 grams of potassium sulfate.