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Ques 1 : Why should a magnesium ribbon be cleaned before burning in air? Ans 1: Magnesium is very reactive metal like (Na, C a, etc.). When it expose to air it reacts with oxygen to form a layer magnesium oxide (Mg O) on its surface.                  Mg +  O 2 → 2 Mg O This layer of magnesium oxide is quite stable and prevents further reaction of magnesium with oxygen. The magnesium ribbon is cleaned by sand paper to remove this layer so that the underlying metal can be used for the reaction. «« Chapter 1 NCERT Solution                                            Next question »»

                    Banking of road The maximum permissible velocity with which vehicle can go round a level curved road without skidding depends on the coefficient of friction ( μ)  between the tyres and the road The value of  μ  decreases when road is smooth or tyres of the vehicle are worn out or the road is wet and so on. Thus force of friction is not a reliable source for providing the required centripetal force to the vehicle. A safer course of action would be to raise outer edge of the curved road shove the inner edge. By doing so, a component of normal reaction of the road shall be spared to provide the centripetal force. This phenomenon of raising outer edge of the curved road above the inner edge is called banking of roads . It's facilitates vehicles to turn without slipping. Three forces are acting on the vehicle as shown in Figure below.  (i) Weight mg of the vehicle acting vertically downwards.  (ii)...

Ques 1 : What do you mean by sports journalism? Ans : In sports journalism we mean that we can gather information regarding all sports activities and to collect all different types of material required for physical education. Such physical education teachers who have skill in communicating by oral or writing can avail their career option in the field of sports journalism.  Ques 2 : What do you mean by Health related careers? Ans : In the modern world, people are more aware of their health and health related issues. Each and every person is curious about their health. He remain to be hale and healthy. He wants to adopt a healthy life style. So there is an increment in job opportunities in health related careers in field of physical education. The no. of health and weight control clubs has increased tremendously. The another career related to health career is athletics training.  Ques 3 : What is the objective of physical education? Ans : The main obje...

Ques : Di nitrogen and dihydrogen react with each other to produce ammonia according to the following chemical equation:                        N 2 ​ +  H 2  ​ (g)→2  NH 3  ​   (i) Calculate the mass of ammonia produced if 2.00×10 2 g di nitrogen react with 1.00×10 3 g of dihydrogen.  (ii) Will any of the two reactants remain un reacted? (iii) If yes, which one and what would be its mass? Ans : (i) 28.0 g of  N 2  require 6.0 g of  H 2  to produce =34.0 g of NH  ​    2.00 × 10³ g of N 2  will produce = 28/34 ×2.00×10³g of  NH 3    =2.43×10³ g of  NH 3                  = 2430 g  NH 3 ​   (ii) Yes, dihydrogen will remain un reacted to some extent.  (iii) Amount of hydrogen that remains un reacted. 28.0 g of N 2  require 6.0 g of  H 2 ​   2.00 g×1...

                    1. Introduction Matter is made up of one or different type of elements. Under normal conditions no other element exists as an  independent atom in nature, except noble gases. However, a group of atoms is found to exist together as one species having characteristic properties. Such a group of atoms is called a molecule. Obviously there must be some force which holds these constituent atoms together in the molecules. The attractive force which holds various  constituents (atoms, ions, etc.) together in different chemical species is called a chemical bond. Since the formation of chemical compounds takes place as a result of combination of atoms of various elements in different ways, it raises many questions. Why do atoms combine? Why are only certain combinations possible? Why do some  atoms combine while certain others do not? Why do molecules possess definite shapes? To answer such questions differen...