Aspirin (C9H8O4) is a drug that can be used to relieve pain or prevent heart attacks. Aspirin is based on traditional medicines made from the willow tree. People have used these medicines for thousands of years. Today, factories make aspirin by mixing salicylic acid (C7H6O3) and acetic anhydride (C4H6O3). When these two substances combine, they form aspirin and acetic acid (C2H4O2). The aspirin is made into pills that are sold as medicine. what is the reactant