Aditya Abeysinghe Presentations

What is the Silver Mirror Test? Silver Mirror Test is a test that is used to differentiate between aldose and ketose sugars using the Tollen's reagent. Tollen's reagent is an alkaline solution of ammoniacal silver nitrate and is used to test for aldehydes. *Ketones do not react with the Tollen's reagent. Silver ions in the presence of hydroxide ions form a brown precipitate of silver (I) oxide, Ag 2 O (s) . Ag 2 O This precipitate dissolves in aqueous ammonia, forming the diamminesilver(I) ion, [Ag(NH 3 ) 2 ] + . The reactions that take place in this experiment are as follows: 2Ag + (aq)  + 2OH - (aq)   →   Ag 2 O (s)  + H 2 O (l) Ag 2 O (s)  + 4NH 3 (aq)  + H 2 O (l)   →  2[Ag(NH 3 ) 2 ] + (aq)  + 2OH - (aq) What happens if Silver Nitrate is used without ammonia or why is ammonia used in this experiment? When ammonia is added to the silver nitrate solution, silver ions are less prone to re...

History -  Before Rutherford, the most widely accepted theory about the distribution of charges and masses on any atom was the Plum pudding model. The plum pudding model explained that ' an atom is a large positively charged body that contained small,free-floating, negatively charged particles called electrons and the atom is neutral since the negative charge of the electrons cancels out with the positive charge of the protons '. How did the plum pudding fail for later research? Ernest Rutherford did similar experiments in which he sent alpha beams or alpha particles over a wide variety of different foils. E.g.: Aluminum, Iron, Lead, Gold etc. However, Rutherford noticed that alpha particles would not behave in similar manner, as is expected according to the plum pudding model, when directed at a gold foil. This led to further research and is popularly called the 'Gold Foil Experiment' or the 'Geiger-Marsden  Experiment'. ...

When a neutral object is charged by induction, the object is charged by the mutual repulsive forces that build up between the neutral object and the charged object, without establishing physical contact between them. How is a neutral object charged using a charged object? For example assume that there’s a neutral sphere and we bring a positive rod near this object. Now remind that an object being neutral is not that it does not have any charges in it. A neutral object is any object where the total no. of positive charges is equal to the total no. of negative charges. As the charged rod approaches the neutral sphere, the negative charges on the sphere are attracted toward the rod and the positive charges are repelled. Note that the sphere is still neutral. When the sphere is grounded by a wire, electrons move up from the earth and give the sphere a net negative charge. When the ground wire is removed there are only negative charges in the sphere. ...