15. In the gaseous phase, which of the following diatomic molecules would be the most polar? (A) LiF (B) CsF (C) NaCl (D) CsCl

21. Given the following acids and Ka values: HOAc HCN HF HClO₄ 1 x 10⁷ 1.76 x 10⁴ 4.93 x 10⁻¹⁰ 3.53 x 10⁻⁸ Which is correct in term of base strength? (A) CN⁻ < F⁻ < OAc⁻ < ClO₄⁻ (B) CN⁻ < OAc⁻ < F⁻ < ClO₄⁻ (C) ClO4- < OAc- < CN- < F- (D) ClO4- < F- < OAc- < CN-