Other ways to search: Events Calendar Campus Map. Introduction A cotton swab is dipped into concentrated hydrochloric acid producing hydrogen chloride gas while a second on is dipped into concentrated aqueous ammonia producing ammonia gas.
Dip one Q-tip into concentrated hydrochloric acid HCl and a second cotton swab into concentrated aqueous ammonia NH3. Simultaneously insert both cotton swabs into the ends of the glass apparatus securing the rubber septa.
Place the glass apparatus on the overhead projector. Wait until a while ring of solid ammonium chloride forms where the hydrogen chloride and ammonia gases meet. The ammonia gas, having a lower molecular weight than the hydrogen chloride, will diffuse faster and travel a greater length of the tube.
With computer programs developed to understand the nature of chemical bonding and structure at the U. Department of Energy's Environmental Molecular Sciences Laboratory on the PNNL campus, the theory and modeling team took that data and used it to gauge how closely the chloride's hydrogen was sidling up to the ammonia's nitrogen when the extra electron is around. The resulting picture showed how losing the surplus electron can cause ammonia and hydrogen chloride to transform into ammonium chloride.
Without electrons, it behaves another way. The researchers solved another riddle as well. Chemists have long wondered about that interaction between that cozy pair, one molecule of ammonia and one molecule of hydrogen chloride. The bond could be either ionic in nature or more like a hydrogen bond, weaker than both ionic and covalent bonds but with characteristics of each.
Comparing the data in the absence and presence of electrons, the theoretical team determined the types of arrangements the nitrogen, hydrogens, and chloride could be in. From these, they concluded the molecules formed a hydrogen bond. Understanding the reaction brings hope that chemistry will have a clean future. Print this page? Page of This creates an electron-adorned ammonium chloride, an ionic salt bottom right. The extra electron may find its way, temporarily, into the ammonium molecule bottom left , forming a Rydberg radical.
This is because hydrogen chloride has almost twice the molecular weight of ammonia, and the rate of diffusion is inversely proportional to the square root of the molecular mass of the gas.
It is worth noting that the rate of diffusion is not the same as the speed at which the gas molecules travel which is hundreds of meters per second. The gas molecules follow a zig-zag path through the tube as they collide with the air molecules in the tube.
The purpose of the glass tube is to eliminate air currents and to see if the gas molecules will move on their own. This collection of over practical activities demonstrates a wide range of chemical concepts and processes.
Each activity contains comprehensive information for teachers and technicians, including full technical notes and step-by-step procedures. Use this practical to investigate how solutions of the halogens inhibit the growth of bacteria and which is most effective. Site powered by Webvision Cloud. Skip to main content Skip to navigation.
Five out of five No comments. If necessary, the tube can be dried by pushing a cotton wool pad soaked in acteone through the tube and leaving it for a few minutes. The concentrated hydrochloric acid and the ammonia solution are easier to handle in small bottles than in Winchesters large bottles for this demonstration. Health, safety and technical notes Read our standard health and safety guidance The demonstrator should wear goggles and protective gloves. Care should be taken when opening the bottle of ammonia solution, particularly on hot days when pressure can build up in the bottle.
If the bottle of ammonia is kept for a long time, its concentration may decrease which will lessen the effectiveness of the demonstration. Procedure Working in the fume cupboard, clamp the glass tube at either end, ensuring that it is horizontal. Open the bottle of ammonia solution cautiously, pointing the bottle away from both you and the audience. Open the bottle of hydrochloric acid and hold the stopper near the mouth of the ammonia bottle.
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