CBSE ADDA

           CBSE Class IX ( 9th) Science         Chapter 4. Structure Of The Atom JSUNI TUTORIAL,  PANJABI COLONY, SAMASTIPUR, BIHAR Multiple Choice Questions ( 1marks)                1 x  5  =  5 marks 1. Which of the following correctly represent the electronic distribution in the Mg atom? (a) 3, 8, 1          (b) 2, 8, 2         (c) 1, 8, 3        (d) 8, 2, 2 2. Rutherford’s ‘alpha (α) particles scattering experiment’ resulted in to discovery of (a) Electron   (b) Proton      (c) Nucleus in the atom       (d) Atomic mass 3. The ion of an element has 3 positive charges. Mass number of the atom is 27 and the number of neutrons is 14. What is the number of electrons in the ion? (a) 13             (b) 10             (c) 14                          (d) 16 4. Elements with valency 1 are (a) Always metals    (b) always metalloids          (c) either metals or non-metals      (d) always non-metals 5. The first model of an atom was given by (a) N. Bohr         

Atoms and molecules Sample Test Paper Time 1 hr M.M.35  (Section A) 10 x 1 = 10 1. The atomic radius of hydrogen atom is a. 0.037 nm b. 0.037 x 10 -9 m c. both a &b d. none 2. Complete the following sentence : In water, the proportion of hydrogen and oxygen is ---------- by mass a. 1:8 b. 3:4 c. 9:0 d. none 3. The actual mass of hydrogen atom  a. 1.673 x 10 -24 g b. 1.673 x 10 c.1u d. both a & b 4. The symbol of cobalt a.C.o. b. CO c. Co. d. none 5. Atomicity of noble gases is one  a. True b. false c. can‟t say d none 6. The molecular mass of sulfuric acid a. 28 u b. 108 u c. 98u d. none 7. What are the number of electron and proton in chlorine ion a. 17p & 18 e b. 18 p & 17 e c. 17 e & 0 e d. none 8. The value of symbol „L‟ a. 6.022 x 10 23 b. 6.022 x 10 -23 c. 0.622 x 10 23 d. none 9. What is the mass of of 0.2 moles of oxygen atoms? a. 2.3 g b. 3.2 g c. .32 g d. none 10. Write the atomicity of CO2 gas a. 2 b. 3 c. 0 d. none (Sect

The first direct experimental evidence for the electrical nature of matter came from the experiments of  Michale Faraday . He showed from his experiments that electricity is composed of particles called ‘atoms of electricity’. It was  George Johnstone Stoney , an Irish Physicist who first proposed the word ‘ electron ‘ for atom of electricity’ in 1891.His contribution to research in this area laid the foundations for the eventual discovery of particles by  J.J. Thomson in 1897. In 1878, Sir William Crooke,  while conducting an experiment using a  discharge  tube, found certain visible rays travelling between two metal electrodes. These rays are known as Crooke’s Rays or  cathode rays . The  discharge  tube used in the experiment is now referred to as Crookes tube or more popularly as Cathode Ray  Tube (CRT). Cathode Ray Tube :  It is a long glass tube filled with gas and sealed at both the ends. It consist of two metal plates (which act as electrodes) connected with hi

Class 09 Subject -Science Atoms and molecules Sample Test Paper Time 1 hr  M.M.35 (Section A) 10 x 1 = 10 1. The atomic radius of hydrogen atom is a. 0.037 nm b. 0.037 x 10 -9 m c. both a &b d. none 2. Complete the following sentence : In water, the proportion of hydrogen and oxygen is ---------- by mass a. 1:8 b. 3:4 c. 9:0 d. none 3. The actual mass of hydrogen atom a. 1.673 x 10 -24 g b. 1.673 x 10 c.1u d. both a & b 4. The symbol of cobalt a.C.o. b. CO c. Co. d. none 5. Atomicity of noble gases is one a. True b. false c. can’t say d none 6. The molecular mass of sulfuric acid a. 28 u b. 108 u c. 98u d. none 7. What are the number of electron and proton in chlorine ion a. 17p & 18 e b. 18 p & 17 e c. 17 e & 0 e d. none 8. The value of symbol ‘L’ a. 6.022 x 10 23 b. 6.02

chemistry adda: 9th chemistry Self-evaluation on Mole concept Sample Problem 1.  Calculate the number of mole in 52 g of Helium. Solution.  We know that, Atomic mass of He = 4u So, its molar mass = 4 g  That is, 4 g of He contains 1 mole of He. Or, 4 g of He = 1 mole of He Or, 1 g of He = 1/4 mole of He So, 52 grams of Helium =1/4 x 52 mole = 13 moles Therefore, there are 13 moles in 52 g of He Sample Problem 2.  Calculate the number of moles for 12.044 X 10 23  atoms of Helium. Solution:  6.022 X 10 23  atoms of Helium           = 1 mole 1 atom of Helium                                 =1/6.022 X 10 23  mole 12.044 X 10 23  atoms of Helium         = [(1/6.022 X 10 23 ) x    12.044 X 10 23   ]moles [ You may use  ----        Number of moles    = (given numbers of particles /Avogadro number)] Sample Problem 3.  How many moles are there in 5 grams of calcium? Sample Problem 4.  How many moles there in 12.044 X 10 23  atoms of phosphorous? Samp

CBSE CHEMISTRY CLASS 9TH CHAPTER - 3 ATOMSAND MOLECULES Download solved paper based on mole concept 9th Mole concept numerical problems solved-CBSE SET- 1 Download File 9th Mole concept numerical problems solved-CBSE SET- 2 Download File practice your learning  1. Calculate the number of moles of magnesium present in a magnesium ribbon weighing 12 g. Molar atomic mass of magnesium is 24g/ mol 2. Verify by calculating that (a) 5 moles of CO 2 and 5 moles of H 2 O do not have the same mass. (b) 240 g of calcium and 240 g magnesium elements have a mole ratio of 3:5. 3. Find the ratio by mass of the combining elements in the following compounds.  (a) CaCO 3 (b) MgCl 2 (c) H2SO4 (d) C2H 5 OH  (e) NH 3   (f) Ca(OH) 2 4. Calcium chloride when dissolved in water dissociates into its ions according to the following equation. CaCl 2 (aq) → Ca 2 + (aq) + 2Cl– (aq) Calculate the number of ions obtained from CaCl 2 when 222 g of it is dissolved in water.