 Good day! Welcome to the first lesson of NSHCO physical science in a series of two lessons. The topic of this lesson is the test for n ions. The objectives of this lesson are to make use of tests to identify aqueous n ions like carbonate, chloride, iodide, nitrate, and sulfate. Let's switch over to hear what Mary and her mom discussed after she came back from a tour at the coast. Welcome back! How was your trip? Fantastic! I brought a bottle of seawater as a canvas. She can do some analysis on this water, can't you? I understand that seawater contains sodium and chloride ions, but I was wondering what other ions are present? Can we do some tests to see what other ions are present? We use different processes and machines to do water analysis, but to test for simple ions we use chemical reagents. I will show you now how it is done. I think we should start with tests for common n ions. What are n ions? n ions are negatively charged ions. We are going to test for carbonate ions, chloride ions, nitrate ions, iodide ions, and sulfide ions. Get your Gregor Pukredi for tests, reagents, and observations. We are going to start the carbonate test. How do we test for carbonate? We test for a carbonate by reacting the given sample with a dilute acid. This can produce effervescence. The gas produced is bubbled through lime water. What is effervescence? Effervescence is bubbling of a gas. Okay, this is like testing for carbon dioxide. Yes, a carbonate reacts with an acid to produce carbon dioxide. If the lime water turns milky, then we can confirm that the solid contains a carbonate ion. Oh, I see. I am going to add some hydrochloric acid to the unknown solid in the test tube. Look, the lime water has turned milky. Does that mean the white solid is carbonate? Yes, this test confirms that the solid does contain a carbonate. Next, let's test for the chloride ion. The sea water you brought should contain chloride ions. Yes, mommy dear, sea water contains table salt, which is sodium chloride. Now, I am going to add a few drops of nitric acid to acidify the solution. And now, I will add silver nitrate to the solution. Wow, a white solid is formed. The solid produced by reacting solutions like this is called precipitate. When a white precipitate is formed in an acidic solution, we confirm that the solution contains chloride ions. Okay. The silver ion of silver nitrate combined with the chloride in the sea water to form the precipitate, which is called silver chloride. According to my table, next to test is sulphate. Yes. To test for sulphate, we again need to add dilute nitric acid. But this time, we add a few drops of aqueous barium nitrate. To the solution labeled unknown, we add a few drops of dilute nitric acid with the medicine dropper. And then we add aqueous barium nitrate with another medicine dropper. Wow. A white precipitate is formed again. Yes. This time, it is the precipitate of barium sulphate. This proves to us that the unknown in iron contains the sulphate in iron. Now, we are going to test for iodide. We will again need to add dilute nitric acid and aqueous lead nitrate. To this unknown in iron, I will add a few drops of dilute nitric acid and then a few drops of aqueous lead nitrate. A yellow precipitate. This is cool, mom. Yes. The yellow precipitate confirms the presence of iodide. Okay. Lastly, we are going to test for the nitrate in iron. We will need aqueous sodium hydroxide, red litmus paper, aluminum foil. Now, let's see. We have sodium hydroxide, the Watt spirit burner, red litmus paper, aluminum foil, the unknown in iron, test tube holder and of course, matches. I will now add a bit of sodium hydroxide into the unknown in iron. Next, I will insert a piece of the aluminum foil into the test tube. I will heat the test tube over the spirit burner. The litmus paper is turning blue. Now, I know how to test for anions. It was great to observe the color changes. I will definitely remember them since I saw the changes myself. Thanks, mom. It's a pleasure, dear. Here is a complete summary of all the tests for the different anions. Let's go through them again. The test for the carbonate in iron. Effervescence and carbon dioxide were produced when dilute hydrochloric acid was added to the solution with the carbonate in iron. The test for the chloride in iron. A white precipitate was produced when dilute nitric acid and aqua-silver nitrate were added to the solution with the chloride in iron. The test for the sulphate in iron. A white precipitate was produced when dilute nitric acid and aqueous barium nitrate were added to the solution with the sulphate in iron. The test for the iodide in iron. A yellow precipitate was produced when dilute nitric acid and aqueous lead nitrate were added to the solution with the iodide in iron. The test for the nitrate in iron. Ammonia was produced when aqua-sodium hydroxide and aluminium foil were added to the solution with the nitrate in iron. And then it was carefully heated. Next time we will do the test for the cations. Goodbye.