Welcome to the NCERT Solutions for Class 9 Science - Chapter Atoms and Molecules. This page offers a step-by-step solution to the specific question from Exercise 4, Question 1: . With detailed answers and explanations for each chapter, students can strengthen their understanding and prepare confidently for exams. Ideal for CBSE and other board students, this resource will simplify your study experience.
Calculate the molecular masses of H2, O2, Cl2, CO2, CH4, C2H6, C2H4, NH3, CH3OH.
Atomic mass includes the masses of three subatomic particles which make up an atom i.e. proton, neutron and electron.
Unit of atomic mass is 'u'
‘u’ = unified atomic mass unit & 1/12 th mass of single carbon-12 atom
‘u’ = 1.66 x 10-24 g
(Just for understanding - Atomic mass approximately equal to twice of atomic no.)
Molecular mass of a substance is the sum of atomic masses of all the atoms in a molecule of a subitance.
Unit of molecular mass = 'u’
Molecular mass of H2 = 2 x 1 = 2u (Atomic mass of H=1)
Molecular mass of O2 = 16 x 2 = 32 u (Atomic mass of O=16)
Molecular Mass of Cl2 = 35.2 x 2 = 71 u (Atomic mass of Cl = 35.5)
Molecular Mass of CO2 = 12 x 1 + 16 x 2
= 12 + 32 = 44 u ( Atomic Mass of C = 12)
Molecular Mass of CH4 = 12 x 1 + 4 x 1
= 12 + 4 = 16 u
Molecular Mass of C2H6 = 12 x 2 + 6 x 1
= 24 + 6 = 30 u
Molecular Mass of C2H4 = 12 x 2 + 4 x 1
= 24 + 4 = 28 u
Molecular Mass of NH3 = 14 X 1 + 3 x 1
= 14 x 3 = 17 u (Atomic Mass of N = 14)
Molecular Mass of CH3OH = 12 x 1 + 4 x 1 + 16 x 1
= 12 + 4 + 16 = 32 u
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Read MoreWelcome to the NCERT Solutions for Class 9 Science - Chapter . This page offers a step-by-step solution to the specific question from Excercise 4 , Question 1: Calculate the molecular masses of H2, O2, Cl2, CO2, CH4, C2H6, C2H4, NH3, CH3OH.....
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