Knowledge hub

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 »»

  Diagonal Relationship between Beryllium and Aluminium The ionic radius of Beryllium (Be 2+) is estimated to be nearly 31 pm; the charge/radius ratio Or e/m ratio is nearly the same as that of the Al 3+ ion. Hence beryllium resembles aluminium in these ways. Some of the similarities are given below: » Like Aluminium, Beryllium(be) is not readily attacked by acids H+ donor because of the formation of an oxide film on the surface of the metal by reacting with oxygen, i.e. they are rendered passive by nitric acid. » Beryllium hydroxide[[Be(OH)4]2] dissolves in excess of alkali to give a beryllate ion, [ Be(OH)4]2– just as aluminium hydroxide[Al(OH)3] gives aluminate ion, [Al(OH)4] » The chlorides of metals beryllium and aluminium have Cl– bridged chloride structure in vapour phase. Both the chlorides are soluble in organic solvents and are strong as Lewis acids They are used as Friedel Craft catalysts. » Beryllium(Be) and aluminium(Al) ions have strong tendency to form complexes, (Be...

                    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 : 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...

                            Charge Charge is that property of an object by virtue of which it apply electrostatic force of interaction on other objects. Charges are of two types (i) Positive charge (+ve)  (ii) Negative charge (-ve)  Like charges repel and unlike charges attract each other.               Quantization of Charge Charge on any object can be an integer multiple of a smallest charge (e).                     Q = ± n e where, n = 1, 2, 3,……. and e = 1.6 * 10-19 C.                   Conservation of Charge Charge can neither be created nor be destroyed. but can be transferral from one object to another object. Recently a new particle has been discovered called ‘Quark’. It contains charge ± e / 3, ± 2e / 3. [The protons and neutrons are combination of other entities called ...