{"news":[{"uid":4160,"title":"Reach for the stars","teasertext":"Boldly go where no one has gone before and participate in the pilot edition of the Swiss Astronomy and Astrophysics Olympiad until May 3 or join the organisation! While this competition is not one of the ten members of the Science Olympiad, we're passing the message to the space explorers among you.","short":"","body":"","datetime":1712650620,"datetimeend":0,"newstype":1,"newstypetext":null,"links":"https:\/\/saao.ch\/","subjects":["Tips"],"image":["https:\/\/science.olympiad.ch\/fileadmin\/_processed_\/6\/3\/csm_Design_ohne_Titel_15_f8e7ca1947.png"],"link":"https:\/\/science.olympiad.ch\/en\/news\/news\/default-1603a5acaf5e07df596f86c9d3266c6b","category":[{"uid":5,"title":"Startseite"},{"uid":4,"title":"Association"}]},{"uid":4095,"title":"Determination of the magnesium and calcium content in effervescent tablets","teasertext":"Are you a teacher looking for experiment ideas? The Chemistry Olympiad is at your service! Our volunteers have broken down an experiment from the final round into three bits suitable for a lesson which will be published here. This is the third and last part.","short":"Are you a teacher looking for experiment ideas? The Chemistry Olympiad is at your service! Our volunteers have broken down an experiment from the final round into three bits suitable for a lesson which will be published here. This is the third and last part.","body":"<p>Duration: ca. 2 h<br \/> Difficulty: High<\/p>\r\n<p class=\"info-box\">A PDF download of this task sheet as well as the answers and instructions for preparing the experiment can be found <a href=\"t3:\/\/folder?storage=1&amp;identifier=%2Fuser_upload%2FArchiv%2FPublic%2FBrain_Food%2FChemistry%2FMore%2FTeaching_Material%2FExperiments%2FExperiments_with_Effervescent_Tablets%2FPart_3%2FEN%2F\">here.<\/a><\/p>\r\n<h2>Materials<\/h2>\r\n<ul> \t<li>1 x 100 ml volumetric flask<\/li> \t<li>1 x 50 ml Burette<\/li> \t<li>3 x 200 ml Erlenmeyer flask<\/li> \t<li>Glass funnel<\/li> \t<li>Glass or Plastic pipettes<\/li> \t<li>Hot plate and stir bar<\/li> \t<li>Mortar and pestle<\/li> \t<li>pH paper<\/li> \t<li>Spatula<\/li> <\/ul>\r\n<h2>Chemicals<\/h2>\r\n<ul> \t<li>0.1 M aqueous sodium hydroxide<\/li> \t<li>0.1 M EDTA solution<\/li> \t<li>2 M aqueous hydrochloric acid<\/li> \t<li>Buffer solution pH 10 (NH4Cl\/NH3)<\/li> \t<li>Deionized water<\/li> \t<li>Eriochrome Black T, 1% in NaCl<\/li> \t<li>Effervescent tablets containing magnesium and calcium<\/li> \t<li>Murexide<\/li> <\/ul>\r\n<h2>Procedure<\/h2>\r\n<h3>Part I: Dissolving the Tablet<\/h3>\r\n<ol> \t<li>Dissolve the 1st effervescent tablet in deionized water in a 100 ml volumetric flask.&nbsp;You may use a mortar and pestle to crush the tablets. Don't fill the volumetric flask&nbsp;up right away but try to add a smaller amount of deionized water initially and swirl&nbsp;to dissolve the tablet. You may add 2 M HCl until the tablet is completely dissolved.<\/li> \t<li>Fill the volumetric flask up to the mark with deionized water.<\/li> <\/ol>\r\n<h3>Part II: Determination of the total divalent cation content<\/h3>\r\n<ol> \t<li>The following operations are carried out using the solution obtained in Part I.<\/li> \t<li>Transfer 10 ml of the solution from the volumetric flask into a 200 ml Erlenmeyer&nbsp;flask. Add 1 ml 2 M HCl and heat the solution to 90\u00b0C for 10 min while stirring.<\/li> \t<li>Let the solution cool to room temperature. Neutralize the solution with 0.1 M&nbsp;aqueous sodium hydroxide until the pH is 7.<\/li> \t<li>You may also dilute the solution a little more using deionized water for better&nbsp;visual monitoring later.<\/li> \t<li>Add 1 ml buffer solution and a very small amount of Eriochrome black T.<\/li> \t<li>Fill a burette with 0.1 M EDTA solution.<\/li> \t<li>Titrate the solution while stirring constantly. A color change from red to blue should&nbsp;occur. The equivalence point is reached when the last hue of red disappears.<\/li> \t<li>Repeat steps 2-7 at least two more times. You should end up with at least three&nbsp;titration results for a tablet.<\/li> <\/ol>\r\n<h3>Part III: Specific determination of individual ion contents<\/h3>\r\n<ol> \t<li>Continue using the tablet solution you prepared in Part I.<\/li> \t<li>Transfer 10 ml of said solution into a 200 ml Erlenmeyer flask. Again, add 1 ml ofM HCl and heat the solution to 90\u00b0C for 10 min while stirring.<\/li> \t<li>Let the solution cool to room temperature. Neutralize the solution with 0.1 Maqueous sodium hydroxide until the pH is 7.<\/li> \t<li>Fill a burette with 0.1 M EDTA solution.<\/li> \t<li>Work quickly now. Carefully add more 0.1 M aqueous sodium hydroxide until youreach a pH of \u2265 12. Monitor with pH paper.<\/li> \t<li>Add a very small amount of murexide with the tip of a spatula.<\/li> \t<li>Titrate the solution with 0.1 M EDTA solution while stirring. A color change from redto violet should occur. The equivalence point is reached when the last hue of reddisappears.<\/li> \t<li>Repeat steps 2-7 at least two more times.<\/li> <\/ol>\r\n<h2>Theoretical questions<\/h2>\r\n<h3>Question 1&nbsp;<\/h3>\r\n<p>Why do we add 2 M HCl and heat the mixture in Parts II and II?<\/p>\r\n<h3>Question 2&nbsp;<\/h3>\r\n<p>Write down the reaction equation for the titration in Part II.<\/p>\r\n<h3>Question 3<\/h3>\r\n<p>Which divalent ion content is determined in Part III and why only this one in Part III?<\/p>\r\n<h3>Question 4<\/h3>\r\n<p>Calculate the individual contents of calcium and magnesium in the tablet.<\/p>\r\n<h3>Question 5<\/h3>\r\n<p>Calculate the individual contents of calcium and magnesium in the tablet.<\/p>\r\n<p class=\"info-box\">Would you like to discover all three parts of the experiment now - and more? You will find what you are looking for in the Chemistry Olympiad <a href=\"t3:\/\/folder?storage=1&amp;identifier=%2Fuser_upload%2FArchiv%2FPublic%2FBrain_Food%2FChemistry%2FMore%2FTeaching_Material%2F\">teaching material archive<\/a>.<\/p>","datetime":1711403460,"datetimeend":0,"newstype":1,"newstypetext":null,"links":"","subjects":["Experiments"],"image":["https:\/\/science.olympiad.ch\/fileadmin\/_processed_\/5\/c\/csm_IMG_2974_3345478c9f.jpg"],"link":"https:\/\/chemistry.olympiad.ch\/en\/news\/news\/determination-of-the-magnesium-and-calcium-content-in-effervescent-tablets","category":[{"uid":3,"title":"Chemistry"},{"uid":5,"title":"Startseite"}]},{"uid":4143,"title":"Register for the Helvetic Coding Contest 2024","teasertext":"Get ready for the biggest competitive programming event in Switzerland, where wizards and witches of code gather to showcase their skills. After 4 years of absence, the Polympiads association is thrilled to announce the return of HC\u00b2, taking place on Saturday, April 13, 2024 at the EPFL campus.","short":"","body":"","datetime":1711011420,"datetimeend":0,"newstype":1,"newstypetext":null,"links":"https:\/\/soi.ch\/blog\/hc2-24","subjects":["Tips"],"image":["https:\/\/science.olympiad.ch\/fileadmin\/_processed_\/3\/8\/csm_23641c51feadb68e8506d2a729612097_f9377346db.jpg"],"link":"https:\/\/science.olympiad.ch\/en\/news\/news\/register-for-the-helvetic-coding-contest-2024","category":[{"uid":9,"title":"Informatics"},{"uid":5,"title":"Startseite"}]}],"offset":3,"hasmore":1}