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3 years ago

as a solid, Cr adopts a body-centered cubic unit cell. How many unit cells are present per cubic centimeter of Cr?

1 answer:

8 0

D(Cr) = 8,96 g/cm3

M(Cr) = 63,546 g/mol 

In a cell face centred cubic, there are 4 atoms of Cur . . . ! 

n(Cr in 1 cm3) = m(Cu) / M(Cr) 
n(Cr in 1 cm3) = 8,96 / 63,546 
n(Cr in 1 cm3) = 0,141 mol of Cr 

Avogadro's number is : NA = 6,02•10^23 mol^-1 

N(Cr) = n(Cu) x NA 
N(Cr) = 0,141 x 6,02•10^23 
N(Cr) = 8,488•10^22 atoms of Cr 

N(cell) = N(Cu) / 4 
N(cell) = 8,488•10^22 / 4 
N(cell) = 2,122•10^22 cells in 1 cm3

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$C_{\frac{6}{4}}H_{\frac{10}{4}}Cl_{\frac{10}{4}}$

$C_{1.5}H_{2.5}Cl_{1}$

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n = $\frac{molar mass}{empirical mass}$

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So, the molecular formula is:

$2\times C_{3}H_{5}Cl_{2} = C_{6}H_{10}Cl_{4}$

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