Question

Chemistry work


Calculate the molar mass of the following substances

a) Ethyne, C2 H2

b) Sulphur molecule, S8

c) Phosphorus molecule, P4 (atomic mass of C – 12, H – 1) (atomic mass of S – 32) (atomic mass of phosphorus = 31)

d) Hydrochloric acid (HCl) (atomic mass of H – 1, Cl – 35.5) e) Nitric acid (HNO3 ) (atomic mass of H – 1, N – 14, O – 16) Convert into mole. (a) 12g of oxygen gas

(b) 20g of water (c) 22g of carbondioxide Calculate the formula unit mass of ZnO, Na2O, K2CO3​

Answer 1

Answer:

The molar masses of all these substances will be equal to the respective molecular masses expressed in g/mol. Now:

(a) Molar mass of ethyne, C2H2 = Mass of C × 2 + Mass of H × 2

= 12 × 2 + 1 × 2

= 24 + 2

= 26 g/mol

(b) Molar mass of sulphur molecule, S8 = Mass of S × 8

= 32 × 8

= 256 g/mol

Answer 2

Molar Mass of Ethyne ,

= Mass of C *2 + Mass of H * 2

= 12*2 + 1*2 = 24+2 = 26g

Molar Mass of Sulphur Molecule ,

= Mass of S*8

= 32*8 = 256g