Question

Al on burning with O2 produces Al2O3 and liberated
807.5KJ/mol.How many atoms of the Al are to be burned to get 100
KJ of energy to be released
​

Answer 1

Given info : Aluminium, on burning with O2 produces Al2O3 and liberated 807.5KJ/mol.

To find : the no of atoms of the Al are to be burned to get 100 kJ of energy to be released.

solution : after burning one mole of Al atoms, 807.5 kJ energy is being released. so heat of combustion of Al is 807.5 kJ/mol.

so no of moles = released energy/heat of combustion

= 100/807.5 = 0.124 mol

no of atoms of Aluminium = no of moles × Avogadro's number

= 0.124 × 6.023 × 10²³

= 0.747 × 10²³

= 7.47 × 10²² atoms

Therefore 7.47 × 10²² atoms are to be burned to get 100 kJ of energy to be released.