Boiling point of water at 750 mm Hg is 9 | Class 12 Chemistry Chapter Solutions, Solutions NCERT Solutions

Question:

Calculate the molecular mass of the following:
(i) H2O
(ii) CO2
(iii) CH4

Answer:

Molecules are made up of atoms & are  quite small, therefore the actual mass of a molecule cannot be detrmined.It is expressed as the relative mass.C-12 isotope is used to express the relative molecular masses of substances.Thus  molecular mass of a substance may be defined as: the average relative mass of its molecule as compared to the mass of carbon atom taken as 12 amu.

(i) H2O:

The molecular mass of water, H2O

= (2 × Atomic mass of hydrogen) + (1 × Atomic mass of oxygen)

= [2(1.0084) + 1(16.00 u)]

= 2.016 u + 16.00 u

= 18.016

= 18.02 u

(ii) CO2:

The molecular mass of carbon dioxide, CO2

= (1 × Atomic mass of carbon) + (2 × Atomic mass of oxygen)

= [1(12.011 u) + 2 (16.00 u)]

= 12.011 u + 32.00 u

= 44.01 u

(iii) CH4:

The molecular mass of methane, CH4

= (1 × Atomic mass of carbon) + (4 × Atomic mass of hydrogen)

= [1(12.011 u) + 4 (1.008 u)]

= 12.011 u + 4.032 u

= 16.043 u


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Comments

  • Tr
  • 2019-10-14 10:45:26

Difference in temp in what ever measure will be the same.no need of adding 273 and subtracting it again


  • Harshitha
  • 2019-08-29 21:26:17

Very easy method Thank you


  • Hasnehena khatun
  • 2019-05-30 19:06:50

Can u show me another method


  • munazza
  • 2019-05-29 21:12:35

Good


  • Shameema
  • 2019-04-25 18:41:01

It's not clear plzz take different method


  • Himanshu
  • 2018-05-30 15:34:28

Write anwers


  • Shambala
  • 2018-05-05 12:43:33

No it's not


  • Tawseef Manzoor
  • 2018-04-30 09:40:15

But the answer on ncert text book is 1.86g


Comment(s) on this Question

Welcome to the NCERT Solutions for Class 12 Chemistry - Chapter . This page offers a step-by-step solution to the specific question from Excercise 1 , Question 10: Boiling point of water at 750 mm Hg is 99.63°C. How much sucrose is to be added to 500 g of wate....