H2S, a toxic gas with rotten egg like sm | 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

  • Komal
  • 2019-05-12 17:55:07

Actually,you had taken 0.0987,instead of 0.987


  • Science
  • 2019-03-21 11:54:52

Pressure at STP is 1 atm And 1 atm = 1.01325 bar Acc. to Henry’s Law p= KHx ⇒ KH = p / x KH = 1.0325/0.0035 = 289.5 bar This is the correct answer


  • ananthu
  • 2019-03-08 22:54:37

I think there is an error in the second last step, insted of .987, .0987 is used


  • ananthu
  • 2019-03-08 22:53:01

molality is .195 means , .195 moles of solute in 1000 g water


  • Gi
  • 2019-02-11 11:04:21

How is p 0.987?


  • Sudip
  • 2018-07-01 15:23:18

How to say that miles of H2S is 0.195 mol


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 6: H2S, a toxic gas with rotten egg like smell, is used for the qualitative analysis. If the solubility....