Allow it to burn for a few moments so when you gently

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Unformatted text preview: t… The gas is likely to be… Goes out completely Carbon dioxide or nitrogen Re- ignites or glows brighter sometimes oxygen accompanied by a “pop” Explodes (in the form of a loud “pop”) but hydrogen does not glow brighter To perform this test, there are only a few things to keep in mind. Be sure the test tube or container is set in a holder; not held by you. If you are holding it and it “pops,” you could be Dakota State University Page 43 of 232 Basic Laboratory Procedures General Chemistry I and II Lab Manual startled into dropping it. Simply take a glowing splint (looks like a tongue depresser), and start it on fire in a Bunsen burner. Allow it to burn for a few moments, so when you gently blow or shake it out, the wood is hot enough to continue to glow. Put the glowing part of the splint into the top of the test tube or container, but do NOT drop it or allow it to touch the liquid (remember you are testing the gas, not the solution). Note the IMMEDIATE reaction of the splint; if you wait too long, there will not be enough oxygen to support the glow, and the splint will give a false-positive for carbon dioxide or nitrogen. Remember that the hydrogen test is an explosion; we must keep it contained. Never use any container other than a test tube unless otherwise instructed to do so. Buret: Like the pipette, the buret is a precision instrument for measuring volumes of liquid. However, the buret is different in two major differences; first, the volume it measures is variable. Secondly, even though the buret is often read to four significant figures as well, it is not quite as accurate as the pipette. Because of human error, there tends to be larger variance in the last significant figure. Careful inspection of the buret reveals that the volume measurements appear to be “backwards”, with 0 at the top, and the maximum volume (we will use mainly 50 mL burets) at the bottom. This is because the buret is designed to show how much volume has been delivered, rather than how much it contains (like a graduated cylinder, for example). There is a special clamp and ring stand for use with burets. Because burets are primarily used for titrations, and titrations usually require the ability to see a color change (indicating the endpoint), when you use a buret, you want to take a ring stand with a white ceramic base. Avoid using these ring stands for anything else, because the more stained they become, the harder they are to use. The clamp has two positions for burets, and is designed to hold the buret(s), and to be very easy to take the burets out of the clamp. This is for safety reasons; you must never fill a buret while it is in the clamp. Notice the valve at the bottom. The valve is open when it is parallel with the buret (vertical), and closed when it is perpendicular (horizontal). Begin by cleaning the buret by standard methods. To fill the buret, take the buret out of the clamp. Check the valve to be sure it is closed. Pour the reagent from a beaker into the top of the buret. A funnel may be used if necessary, but is discouraged Dakota State University Page 44 of 232 Basic Laboratory Procedures G...
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