Question

Calculate the number of calcium ions in $3.2$ g of calcium oxide $(Ca=40)$.

• A. $1.393\times {10}^{23}$ ions
• B. $6.023\times {10}^{23}$ ions
• C. $3.011\times {10}^{23}$ ions
• D. $0.344\times {10}^{23}$ ions

Answer 1

The correct option is D $0.344\times {10}^{23}$ ions

Molecular weight of $CaO$ $=40+16=56$ g
$56$ g of $CaO$ contains $=6.02\times {10}^{23}$ ions of calcium.
$3.2$ g of $CaO$ contains $=\frac{3.2\times 6.02\times {10}^{23}}{56}=0.344\times {10}^{23}$ ions of calcium