1.

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

Answer»

40
20
28
12

Solution :`underset(1 "mol"^3 (2g) ) (MCO_3) overset(DELTA)(to) underset(22400 "cc")(MO + CO_2)`
448 cc of `CO_2` is evolved from `MCO_3 = 2g`
22400 cc of `CO_2` will be evolved from
`MCO_3 = (2)/(448) xx 22400 = 100 G`
or molecular mass of `MCO_3 = 100 g "mol"^(-1)`
If M is the atomic mass of METAL
`M + 12 +3 xx 16 = 100`
` therefore M = 100 - 12 - 48= 40 `
Equivalent wt.= atomic mass / valency= 40/2 = 20


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