Give the chemical equation for the reaction of phenylamine with propanoic anhydride to form N-phenylpropanamide. In your equation, use the skeletal formula for the organic product N-phenylpropanamide.

N-phenylpropanamide can also be prepared by reacting phenylamine with propanoyl chloride. Explain why propanoic anhydride is chosen in preference to propanoyl chloride in industrial and laboratory preparations.

State the physical property that is measured to check the purity of the N-phenylpropanamide crystals. State two ways in which the measurement would indicate that the product contains impurities.