Question

Determine the number of particle , number of moles and mass , show the law of conservation of mass is observed

4Al + 3O₂   →    2Al₂O₃

(molar mass of  O = 16 g/mol   Al= 27g/mol)

Answer 1

Number of particles

Two formulae units Al2​O3​ form 4 atoms of Al and 3 molecules of O2​ Number of moles, and mass

From the law of conservation of mass;

$4Al+3O_2\to2Al_2O_3$

$4molesAl$ ${({27.0Al\over 1molAl}) }$ $=108gAl$

$3mol O_2$ $({32.0gO_2\over 1mol O_2})$ $=96.0gO_2$

$Reactants_{Total Mass}$ =$108g+96g=204.0g$

$\therefore$ $204.0g Al_2O_3$ are produced

$2moles$ $Al_2O_3$ $({102gAl_2O_3\over 1mole Al_2O_3})$ $=204.0g Al_2O_3$

Law of conservation of mass

$204.0g Reactants=204.0g Products$