Calculate the molar mass of the following substances.

(a) Ethyne, C 2 H 2

(b) Sulphur molecule, S 8

(c) Phosphorus molecule, P 4 (Atomic mass of phosphorus = 31)

(d) Hydrochloric acid, HCl

(e) Nitric acid, HNO 3

 

Answer

Molar mass of C = 12g

Molar mass of H = 1g

Molar mass of S = 32g

Molar mass of P = 31g

Molar mass of Cl = 35.5g

Molar mass of N = 14g

Molar mass of O = 16g

 

(a) Ethyne, C 2 H 2

Molar mass of C 2 H 2 = 2 x Molar mass of C + 2 x Molar mass of H

                                  = 2x 12g + 2 x 1g

                                  = 24g + 2g

                                  = 26g

 

(b) Sulphur molecule, S 8

Molar mass of S 8 = 8 x Molar mass of S

                              = 8x 32g

                              = 256g

 

(c) Phosphorus molecule, P

Molar mass of P 4 = 4 x Molar mass of P

                              = 4 x 31g

                              = 124g

 

(d) Hydrochloric acid, HCl

Molar mass of HCl = 1 x Molar mass of H + 1 x Molar mass of Cl

                                  = 1x 1g + 1 x 35.5g

                                  = 1g + 35.5g

                                  = 36.5g

(e) Nitric acid, HNO 3

Molar mass of HNO 3 = 1 x Molar mass of H + 1 x Molar mass of N + 3 x Molar mass of O

                                  =1x 1g + 1 x 14g + 3 x 16g

                                  = 1g + 14g + 48g

                                  = 63g

  1. Class 9
  2. Chapter 3 Class 9 - Atoms And Molecules (Term 2)

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CA Maninder Singh
CA Maninder Singh is a Chartered Accountant for the past 11 years and a teacher from the past 11 years. He teaches Science, Accounts and English at Teachoo