13. Balance the following equation: BO3(s) + HF(1) BF3(g) + HO(l) A. B0(s) + 6HF(1) 2BF3(g) + 3HO(1) B. B0(s) + HF6 (1) BF(g) + HO (1) C. B0(s) + 2HF(1) 2BF3(g) + H2O(/) D. B0(s) + 3HF(1)2BF3(g) + 3HO(l) E. B0(s) + 6HF(1) 2BF (g) + 6HO(1) 23. The composition of materials such as alloys can be described in terms of mole percentage (mol %), atom percentage (at %), or weight percentage (wt%). Carry out the following conversions among these units. (a) 60 wt% Cu and 40 wt% Al to atom %, A. Cu 30%, Al 70% B. Cu C. Cu D. Cu 45%, Al 55% 50%, Al 50% 55%, Al= 45% E. Cu 40%, Al 60% 24. Potassium fluoride is used for frosting glass. Calculate the molarity of a solution prepared by dissolving 78.6 g of KF in enough water to produce 225 mL of solution. A. 0.304 M B. 0.349 M C. 1.35 M D. 3.29 M E. 6.01 M 25. What volume of concentrated (14.7 M) phosphoric acid is needed to prepare 25.0 L of 3.0 M HPO4? A. 0.20 L B. 0.57 L C. 1.8 L D. 3.6 L E. 5.1 L 26. Copper(II) bromide is used as a wood preservative. What mass of CuBr2 is needed to prepare 750.0 mL of a 1.25 M solution? A. 134 g B. 209 g C. 372 g D. 750 g E. 938 g 27. How many grams of solute are present in this solution: 37.2 mL of 0.471 M HBr A. 2.42 g HBr B. 1.42 g HBr C. 0.22 g HBr D. 3.44 g HBr E. 1.66 g HBr