Question

What volume of 0.16 M NaOH (aq) solution at 25 °C is needed to dissolve 1.25×102 mg of calcium hydroxide? The Ksp of calcium hydroxide is 8.0×10-6 and its molar mass is 74.1 g/mol.

A) 8.8 L

B) 5.4 L

C) 2.6 L

D) 4.2 L

E) 8.4 L

Answer 1

Solution Nach is completely lonized as Naot [Nao H] = conc. of ot ion Nat tot Oolom in solution is 0.16M. Tye expmeli07 3, k sp a1, Ca(OH), - Ksp = [cat] [or] 2 3 The product [ea2+] . [OH-]2 in solution. cannot exceed soox 106 moß. i 3 i [ca 2+ ].[OH J2 = 8.0x10-6 mor. 13 [cat] =800x106 [OH-]? = 8.0x106 moße (0.16 mol. 1-1,2 [cart] = 3,125 x 10-4 mol.it so, solubility of calcium Hydroxide in 0.16M Naoh solution is 3.125 x 109 - moloer I And in this question we have to dissolve, 1.25 x 10 mg of Ca (OH),

I no. of moles of Cacol : = mass of CaCOH molar mass of cacolt) Echos (1000mg = lg) =lo 10.25 x10 mg = 0.0016g mol 1000 mg/g a 74olgl mot 3.1258.104 mol of cacOH, dissolve in IL of Naot solution so, 0.0016g mol of Ca (OH), dissolve in LiL x 0. 00169 moll 1 30125 x 10 4 mol of Mao y Solution. = 504 L of NAOH Solution so option (B) is correcto is 5.4L of 0.16M Naot solution of 25°C needed to dissolve 1.25 x 10² mg of calcium Hydroxide.