Convert ethanol to bromoethane by nucleophilic substitution using NaBr in presence of concentrated H2SO4. React bromoethane with ethanolic solution of KCN to get propanenitrile, CH3CH2CN. Reduce the nitrile by reacting with concentrated H2SO4 to obtain propanoic acid.

Find no. Moles of Silicon by dividing mass by Ar. Then, multiply the result with the Avogadro's Constant.