Question

The equivalent mass of a trivalent metal element is 9 g eq^-1 the molar mass of its anhydrous oxide is …… 

(a) 102 g 

(b) 27 g 

(c) 270 g 

(d) 78 g

Answer 1

(a) 102 g

Let the trivalent metal be M^3+.

Equivalent mass = (mass of the metal) / (valance factor) 

9g eq^-1 = mass of the metal / 3 eq 

Mass of the metal = 27 g 

Oxide formed M₂ O₃ 

Mass of the oxide = (2 × 27) + (3 × 16) 

= 102 g