45. Which is the strongest acid in dilute aqueous solutions? (A) HNO₃ (B) HCl (C) HBr (D) HClO₄ (E) All have the same acidity in aqueous solution.

4. Both ZnS and CaF₂ have a face-centered cubic unit cell where the S²⁻ and Ca²⁺ ions are closest packed in each structure. Which of the following is true? (A) There are 4 tetrahedral holes empty in each structure. (B) In both compounds, one-half of the tetrahedral holes are filled. (C) In both compounds, all the tetrahedral holes are filled. (D) There are 8 Zn²⁺ ions and 4 F⁻ ions in the unit cell. (E) In ZnS, one-half of the tetrahedral holes are filled by Zn²⁺ ions, whereas in CaF₂ all the tetrahedral holes are filled with F⁻ ions.

45. Which is the strongest acid in dilute aqueous solutions?
(A) HNO₃
(B) HCl
(C) HBr
(D) HClO₄
(E) All have the same acidity in aqueous solution.

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