Calculate the molar mass of the following substances. (a) Ethyne, C2H2 (b) Sulphur molecule, S8 (c) Phosphorus molecule, P4 (atomic mass of phosphorus = 31) (d) Hydrochloric acid, HCl (e) Nitric acid, HNO3.

Q.6:- Calculate the molar mass of the following substances.
(a) Ethyne, C2H2
(b) Sulphur molecule, S8
(c) Phosphorus molecule, P4   (atomic mass of phosphorus = 31)
(d) Hydrochloric acid, HCl
(e) Nitric acid, HNO3.

 

Answer:-

(a) Molar mass of C2H2 = 2 x atomic mass of C + 2 x atomic mass of H

=(2 x 12 + 2 x 1)u = (24 + 2)u =26u



 

(b) Molar mass of  S8 = 8 x  atomic mass of  S

= (8 x 32)u = 256u

 

(c) Molar mass of  P4 = 4 x atomic mass of P

= (4 x 31)u = 124u

 

(d) Molar mass of HCl =  atomic mass of H + atomic mass of Cl

= (1 + 35.5)u = 36.5u

 

(e) Molar mass of HNO3 = atomic mass of H + atomic mass of N + 3 x atomic mass of O

= (1 + 14 + 3 x 16)u = (1 +14 +48)u = 63u



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