A 100% pure sample of a divalent metal carbonate weighing 2 g on complete thermal decomposition releases 448 cc of carbon dioxide at STP. The equivalent mass of the metal is

Options

A. 40
B. 20
C. 28
D. 12

Answer

B

Explanation

Divalent metal carbonate means `MCO_(3)`
`underset("1 mol")(MCO_(3))overset(Delta)rarrMO+underset("22400 cc")(CO_(2))`
`"448 cc CO"_(2)` is evolved from `MCO_(3)=2g `
`therefore" 22400 cc CO"_(2)` will be evolved from `MCO_(3)`
`=(2)/(448)xx22400=100g`
`therefore" Molcular mass of "MCO_(3)=100`
If m is the atomic mass of M, `m+12+48=100`
or `m=40`
As metal is divalent, equivalent wt. `=(40)/(2)=20`