The structural formula for sodium stearate, a type of soap, is CH3(CH2)16COO-Na+. It consists of a long hydrocarbon chain (C18H35) attached to a carboxylate group (-COO-) and a sodium ion (Na+). The hydrocarbon chain is nonpolar and hydrophobic, while the carboxylate group is polar and hydrophilic. This dual nature of soap molecules allows them to dissolve both in water and in oil, which is what gives them their cleaning properties.