Exercise: Which of the following is an acid? CH3CH2CH3 HNO3 NH3 Zn(OH)2   Answer: The nitric acid HNO3 is acidic. The H atom is bonded to an oxygen atom in the molecule. This bond can be broken to form a proton, H1+ and a nitrate ion, NO3 1-   CH3CH2CH3 The H-C bond is relatively strong and nonpolar. The hydrogens in the propane molecule are not acidic.   NH3 The H-N bond is relatively strong and polar. The hydrogens in ammonia molecule are not acidic   Zn(OH)2The H-O bond in hydroxide ions is relatively strong and polar. The hydrogens in hydroxide ion are not easily removed to form an oxide ion, O2-. The hydrogen in hydroxide is not acidic.