Question

3.7g of oxide of a metal was heated with charcoal. The liberated carbon dioxide was absorbed in NaOH solution and weighed 1.0g. If the specific gravity of the metal is 0.095cal/g the exact atomic mass of the metal is

• A. 170.8
• B. 32.7
• C. 67.37
• D. 65.4

Answer 1

The correct option is D 65.4

Weight of $C{O}_2$ = 1.0g
Weight of oxygen in oxide = Weight of oxygen in Carbon dioxide $=\frac{32}{44}\times 1=0.727g$
Mass of metal oxide = 3.7g, Mass of oxygen = 0.72g, so mass of metal = 3.7-0.72 = 2.973g.
Eq. Mass of metal $=\frac{2.973}{0.727}\times 8=32.7$
App. Atomic mass $=\frac{6.4}{Sp.heat}=\frac{6.4}{0.095}=67.36$
$n=\frac{App.Atomicmass}{Eq.mass}=\frac{67.36}{32.7}\approx 2$
Exact atomic mass = 32.7 $\times$ 2 = 65.4