19. Select two substances with a molecular structure and a polar covalent bond. 1) CH_(3)COOH 2) KNO_(3) 3) C_(3)H_(8) 4) I_(2) 5) MgO Answer (score: 1):

The correct answer is 1) and 3) . (acetic acid) has a polar covalent bond between the carbon and oxygen atoms in the carboxyl group (-COOH). The oxygen atom is more electronegative than the carbon atom, resulting in a polar covalent bond. (propane) has polar covalent bonds between the carbon and hydrogen atoms. The carbon atoms are more electronegative than the hydrogen atoms, resulting in polar covalent bonds.The other substances listed do not have polar covalent bonds:- (potassium nitrate) has ionic bonds between the potassium and nitrate ions.- (iodine) has a nonpolar covalent bond between the two iodine atoms.- (magnesium oxide) has an ionic bond between the magnesium and oxygen ions.