1.

Iron exhibits bcc structure at room temperature. Above 900^@C, it transforms to foc structure. The ratio of density of iron at room temperature to that at 900^@C (assuming molar mass and atomic radius of iron remains constant with temperature) is ..........

Answer»

`(SQRT3)/(sqrt2)`
`(4sqrt(3))/(3sqrt(2))`
`(3sqrt(3))/(4sqrt(2))`
`1/2`

Solution :For bcc LATTICE `: Z = 2, a = (4r)/(sqrt3)`
For fcc lattice `: Z = 4, a = 2sqrt(2)r`
`(d_(R.T))/(d_(900^@C)) = (((ZM)/(a^3N_A))_("bcc"))/((ZM)/(a^3N_A))_("fcc") = 2/4((2sqrt(2)r)/((4r)/(sqrt3))) = (3sqrt(3))/(4sqrt(2))`


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