Question

Calculate the number of $Ca$ atom present in 0.041 g of $CaO$.

Answer 1

Mole fraction of $Ca$ in $CaO$

Molar mass of $CaO=40+16=56$

Mole fraction= $\frac{40}{56}$

Now, moles of $CaO$ in $0.041g=\frac{0.041}{56}=0.000732$

Total atoms are present in given mole= $0.000732\times 6.02\times {10}^{23}$

Atoms of $Ca=\frac{40}{56}\times 0.000732\times 6.023\times {10}^{23}$

$=0.714\times 7.32\times 6.023\times {10}^{19}$

$=3.14\times {10}^{20}$