 You likely know that sodium chloride is soluble in water. Can you think of other soluble salts? Pause, think, and continue when ready. Copper II sulfate is another soluble salt as it readily dissolves in water to form a solution. Grab your pencil. You can feel the pencil in your hand because a chemical message is relayed from the muscle in your hands to your brain. Potassium chloride plays an important role in nerve conduction. Without it, no chemical messages would be relayed. How would you know if a salt is soluble in water or not? Just from its formula or from its constituent ions. This is actually possible. There are certain trends observed when it comes to the solubility of certain salts. All nitrates are soluble. These are salts containing a nitrate ion such as sodium nitrate and silver nitrate. All chlorides, bromides, and iodides are soluble except for lead and silver. Remember that because silver halides are insoluble we use this to test for the presence of halides. We can distinguish between the different silver halides because they each have a characteristic color and behave differently in the presence of concentrated or dilutamonia. All sulfates are soluble except for lead and barium and calcium. In fact, barium sulfate is so insoluble that it can be ingested and passed through our gastrointestinal tract without being absorbed by our bodies. This is because it is radio opaque just like your bones. This means that x-rays cannot pass through them and because of this an x-ray image of your gastrointestinal tract can be produced. All carbonates are insoluble except for sodium, potassium, and ammonium. Hydroxides are also insoluble except for sodium, potassium, and ammonium. We can also say that all sodium, potassium, and ammonium salts are soluble. Calcium hydroxide is mildly soluble in water. The solution is known as lime water and is used to test for carbon dioxide. If you've ever looked closely at lime water there is a white precipitate at the bottom of the container. This is solid calcium hydroxide. Now that you are familiar with these solubility rules try to determine which of the following salts are soluble in water. Calcium carbonate, magnesium hydroxide, potassium iodide, lithium nitrate, lead bromide. Pause the lesson and continue when ready. The answer is of the five listed salts only potassium iodide and lithium nitrate are soluble in water. Although it is recommended that you learn these solubility rules chemists have combined this data into a table called the solubility table. Why is this important you might ask? Imagine you had to x-ray your gastrointestinal tract and were given a solution of barium chloride instead of a suspension of barium sulfate. Barium ions are inherently toxic and this could lead to many complications and even death. Hard water is water that contains calcium and magnesium ions. This is an issue because we know that they form insoluble salts. This can be seen as limescale or calcium carbonate deposits around water faucets or at the bottom of your water kettle. These ions also make it difficult for soap to lather. Hard water is treated by exchanging the calcium and magnesium ions with sodium and potassium ions through an ion exchange resin. As all sodium and potassium salts are soluble in water, the hard water is now softened. To summarize, the solubility of a certain salt can be determined if we know the solubility rules.