Copper crystallizes in a face centred cubic lattice. Calculate the number of unit cells in 1.2 g of copper. Atomic mass of copper = `63.5mu`.

Explanation

Z (f.c.c.c lattice) = 4, Molar mass of copper
`=63.5"mol"^(-1)`
`N_(A)=6.022xx10^(23)"mol"^(-1)`
Mass of 1 atom of copper
`=(63.5"g mol"^(-1))/(6.022xx10^(23)"mol"^(-1))`
`=1.05xx10^(22)g`
Mass of one unit cell (f.c.c.) of copper
`=4xx1.05xx10^(22)g`
`=4.2xx10^(22)g`
`therefore` No. of unit cells in 12 g of copper
`=(12g)/(4.2xx10^(-22)g)=28.5xx10^(22)`