Question

Calculate the number of moles present in 

(a) 60 g of calcium. 

(b) 3.011 × 10²³ number of oxygen atoms. 

[Given that Ca = 40 u; Avogadro number, NA = 6.022 × 10²³ per mole] 

Answer 1

(a) Number of moles of Ca = Given mass of calcium / Molar mass of calcium = 60 / 40 = 1.5 moles 

(b) Number of moles = Given number of molecules / 6.022×10²³ = 3.011×10²³ / 6.022×10²³ = 0.5mol