Question

Calculate the number of unit cell in 8.1 gram of aluminium if it crystallizes in fcc structure atomic mass = 27 gram per mole

Answer 1

he weight of one mole of a substance is equal to its atomic mass in grams , therefore1 mole of Al =27g=27g of AluminiumAlso , 1 mole contains Avogadro number of atoms1mole=6.023×10231mole=6.023×1023 atoms of AluminiumTherefore1 mole of Al - 27 g of aluminium - 6.023×10236.023×1023 atoms of aluminiumNumber of atoms in 8.1g8.1g aluminium is =(8.1×6.023×1023)/27=(8.1×6.023×1023)/27The face centered cubic structure contains 4 atoms in one unit cell .Therefore , the number of unit cells that has (8.1×6.023×1023)/27(8.1×6.023×1023)/27 atoms of Aluminium can be obtained as ,(8.1×6.023×1023)/(27×4)=4.516×1022

Answer 2

Hey !!

n = given mass/molar mass

    = $\frac{8.1}{27} mol$

Number of atoms = 8.1/27 × 6.022 ×× 10²³

Number of atoms in one unit cell = 4 (fcc)

Number of unit cell = [8.1/27 × 6.022 × 10²³]

    FINAL RESULT = 4.5 × 10²²

GOOD LUCK !!