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

(i) Calculate the number of electrons wh | Class 11 Chemistry Chapter Structure of Atom, Structure of Atom 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

Shahin
2020-04-28 09:45:44

Thanks...

Priya nayak
2019-10-20 10:11:59

Thanks for the solution

Anant
2019-09-20 14:11:39

Mass of e is 9.1 x 10^31 kg

Siddhu
2019-08-11 21:28:30

Mr/Mrs cha,it's not necessary to take the mass of electron in kg only. We know that the mass of electron is 9.1*10^-28g or 9.1*10^-31kg so the solved question is right

GANDHASIRI KIRANKUMAR
2019-08-09 10:23:18

Super

Cha
2019-06-29 20:03:47

Mass of electron should be in kg

Cha
2019-06-29 19:56:04

Mass of a electron is wrong here.It should be 9.1x 10^-31

Sneha
2019-06-20 16:07:26

Thnks alot

Nice
2019-06-14 10:25:01

ððð

Vansh Tyagi
2019-06-12 15:00:32

But mass of electron is 9.1 Ã10(-34)

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Welcome to the NCERT Solutions for Class 11 Chemistry - Chapter . This page offers a step-by-step solution to the specific question from Excercise 1 , Question 1: (i) Calculate the number of electrons which will together weigh one gram. (ii) Calculate the mass a....

(i) Calculate the number of electrons wh | Class 11 Chemistry Chapter Structure of Atom, Structure of Atom NCERT Solutions

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