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Q21. Consider the reaction: 3Ca(OH)2(aq)+2H3PO4(aq)Ca(PO4)2(aq)+6H2O(i) How many millilitres of 0.650MCa(OH)2 solution are needed to neutralize completely 50.0 mL of 0.800MH3PO4 solution? a) 70.6mL b) 92.3mL c) 23.1mL d) 58.8mL e) 46.2mL Q22. A solution is prepared by mixing 25.0g of naphthalene (C1H8) with 0.750L of liquid CS2 (density =1.263g/mL ). What is the concentration of naphthalene in parts per million (ppm)? a) 7.34104ppm b) 5.01104ppm c) 2.57104ppm d) 2.96104ppm c) 4.62104ppm Q23. A 10.00g of an organic compound is dissolved in 50.00g of benzene (kr=6.940C/m). The freezing point of the solution is 1.280C below that of pure benzene. What is the molar mass of the compound? a) 1084g/mol b) 2169g/mol c) 1627g/mol d) 3253g/mol e) 776.5g/mol Q24. The empirical (simplest) formula of a compound with the composition of 67.56%C, 9.94%H, and 22.50%O is a) C4H2O b) C8H6O2 c) C7H2O d) C5H3O2 e) C2H5O Q25. The total number of orbitals in the n=3 principal energy level is: a) 4 b) 9 c) 1 d) 7 e) 16 Q26. The mass percent of ammonia, NH3, in an aqueous solution is 28.9% and density of solution is 0.896g/mL. What is the molarity of the ammonia solution? a) 14.1M b) 12.0M c) 15.2M d) 16.2M e) 9.94M