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

Calculate the mass of a non-volatile sol | 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

Pankaj
2019-05-24 11:24:16

Give the complete & correct solution, immediately

Tanya
2019-05-04 12:11:11

This solution is quite easy but this is not correct. The correct answer for this question is 10.

Tanya
2019-05-04 12:09:55

This is quite easy but correct answer is 10

Bhagya
2019-04-25 10:54:30

For the answer to be 10 , it should be equated with X of solute i.e. ((w1/M1)/(w1/M1)+(w2/M2))

Gautam
2019-04-22 22:21:37

Correct is 10

Neha
2019-03-28 23:44:30

But answer is 10

Neha
2019-03-28 23:43:03

Give the correct solution

Renuka
2019-03-10 23:58:19

Answer is right

Malavika Manish
2019-03-09 15:07:11

The answer is wrong ....the correct answer should be done like given below if vapour pressure of pure liquid is = Po 80 % of pure liquid Ps= 80ÃPo/100 = 0.8Po Ps =Po Ã Xsolute mass of solute = x gram mass of solvent = 114g Molar mass of solute= 40 g/mol Molar mass of solvent (octane C8H18) = 114g/mol Number of moles of solute = x/40 = 0.025x Number of moles of solvent = 114/114= 1 moles Mole fraction of solvent = 1/(1+0.025x) 0.8Po=PoÃ1/(1+0.025x) Cross multiply we get (1+0.025x))0.8Po= Po Divide by 0.8 Po we get 1+0.025x = 1.25 Subtract 1 both side we get 0.025x = 0.25 Now divide by 0.025 we get x = 10g

nikhil gupta
2019-01-17 15:37:35

this answer in wrong instead the formula used will be p-ps/ps

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 2 , Question 18: Calculate the mass of a non-volatile solute (molar mass 40 g mol-1) which should be dissolved in 114....

Calculate the mass of a non-volatile sol | Class 12 Chemistry Chapter Solutions, Solutions NCERT Solutions

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