On the basis of quantum numbers, justify | Class 11 Chemistry Chapter Classification of Elements and Periodicity in Properties, Classification of Elements and Periodicity in Properties 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

Swastika
2019-11-30 06:09:21

Thank u so much sir for u good and valuable an swear

Gayatri Mishra
2019-11-25 18:57:33

Thanx useful

Neha
2019-09-17 21:20:32

Thank u our chemistry sir is taking questions only from this site now i am topper in chemistry thanks for Ur lovable help

Shomil singh
2019-07-09 20:41:20

Thankuu this is very useful

Harsh rao
2018-09-05 20:01:31

It is very helpfull thanxxxx a lot

Pawan rajput
2018-07-03 00:31:37

Thanku

Ayush Pratap Singh
2018-02-25 15:38:16

for people who are confused that why are there 0,1,2,3,4 orbitals instead of 0,1,2,3,4,5 it is because the formula for l=n-1 doesn't tell the sub-shells of the shell, but it tells the NUMBER OF ORBITALS in each shell. example- taking n=5, l should have n-1=4 NUMBER OF SUB-SHELLS i.e 0,1,2,3 and not 0,1,2,3,4

Shivani
2017-08-25 22:47:45

The value of l should be 0,1,2,3 There's no point of putting 4 as we have s,p,d and f orbitals only

shivangi
2017-08-05 06:47:51

L =0 to (n-1) then its value should be 0 1 2 3 4 5

Nikhil
2017-06-24 14:04:33

If n=6 then l should be 0,1,2,3,4,5

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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 4: On the basis of quantum numbers, justify that the sixth period of the periodic table should have 32 ....

On the basis of quantum numbers, justify | Class 11 Chemistry Chapter Classification of Elements and Periodicity in Properties, Classification of Elements and Periodicity in Properties NCERT Solutions

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