CBSE Area

  Guess Questions 2nd Summative Assessment 2012-13 SET-01 [Chemistry] 1. Calculate number of moles in 34 g of NH3 (Given atomic mass of N= 14 u; H= 1 u)?[2] 2. Write chemical formulas of :(a) Sodium Carbonate (b)Ammonium Chloride[2] 3. (a) Write a chemical formula of a compound using zinc ion and phosphate ion. (b) Calculate the ratio by mass of atoms present in a molecule of carbon dioxide (Given C=12, O=16)[2] 4. (a) State the law of Definite proportion with an example.(b)  Give any two limitations of Dalton�s Atomic Theory.         [3] 5. Calculate number of atoms in 120 g of Ca :( atomic mass of Ca= 40u) [3] 6. (a)Write the symbol and name of the element having 14 protons. (b) Complete the table. Element Atomic No Mass No Proton Neutron Cl 17 - - 18 Si - 28 - - F - - 9 10 (c) Give one drawback of Rutherford model. [3] 7 .(a)The average atomic mass of a sample of an element X is 16.2u.What ...

QUESTIONS BANK CBSE BOARD PAPER  Questions:   If K and L shells of an atom are full, then what would be the total number of electrons in the atom ? What is the valency of this element ? Questions:   List three main features of Rutherford�s nuclear model of an atom. Questions:   On the basis of the number of protons, neutrons and electrons in the samples given below identify    (a) the cation     (b) the pair of isobars and            (c) the pair of isotopes. Sample Protons Neutrons Electrons A 17 18 16 B 18 19 18 C 17 20 17 D 17 17 17 Questions:   Composition of the nuclei of two atomic species A and B are given as under : Particala A B Protons 17 17 Neutrons 18 20 (i) What are the mass numbers of A and B ?    (ii) How are they related to each other ? Questions:   (i) Draw a sketch of Bohr�s model of an atom with three shells...