F. Answer in detail. 1. Write the postulates of modern model of atom. 2. Make a note of Thomson's experiment on cathode ray tube. 3. Write two uses of paper chromatography,
Answers
Answer:
Ans:1 Atoms can neither be created nor destroyed. Also, atoms cannot be divided into further small particles. Atoms of different elements can combine with each other in fixed whole-number ratios and form compounds. Atoms can be rearranged, combined, or separated during the process of chemical reactions.
Ans:2 Cathode ray experiment was a result of English physicists named J. J. Thomson experimenting with cathode ray tubes. During his experiment he discovered electron and it is one of the most important discoveries in the history of physics. He was even awarded a Nobel Prize in physics for this discovery and his work on the conduction of electricity in gases.
Procedure of the Experiment
1) Apparatus as set up by providing a high voltage source and evacuating the air to maintain the low pressure inside the tube.
2)High voltage is passed to the two metal pieces to ionize the air and make it a conductor of electricity.
3)The electricity starts flowing as the circuit was complete.
4)To identify the constituents of the ray produced by applying a high voltage to the tube, the dipole was set up as an add-on in the experiment.
5)The positive pole and negative pole was kept on either side of the discharge ray.
6)When the dipoles were applied, the ray was repelled by the negative pole and it was deflected towards the positive pole.
This was further confirmed by placing the phosphorescent substance at the end of discharge ray. It glows when hit by discharge ray. By carefully observing the places where fluorescence was observed, it was noted that the deflections were towards the positive side. So the constituents of the discharge tube were negatively charged.
Uses of Cathode Ray Tube
1)Used as a most popular television (TV) display.
2)X-rays are produced when fast-moving cathode rays are stopped suddenly.
3)The screen of a cathode ray oscilloscope, the monitor of a computer, are coated with fluorescent substances. When the cathode rays fall of the screen pictures are visible on the screen.
Ans:3 1) Qualitative analytical chemistry technique for identifying and separating colored mixtures like pigments.
2)It is used in scientific studies to identify unknown organic and inorganic compounds from a mixture.
Explanation:
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