Question

23. A 5.0 x 104 M solution of MnSO, is gradually made more basic by adding NaOH. At what pH will manganese(II) hydroxide begin to precipitate at 25°C? The Kp of Mn(OH)2 is 2.0 x10-19. A) 4.70 B) 9.30 C) 9.40 D) 4.60 E) 9.57 24. Which of the following substances is most likely to exhibit liquid-crystalline behavior? A) NEC- (CH))CH3 NH.SCN (ammonium thiocyanate) B) CH3 C) CH3-CHz-C-CH2-CH3 CH3 D) E) O`NA

Answer 1

Answer 23 Mn(OH)2 Mn2+ + 2OH- To begin Precipitation, Ksp (Mn(OH)2 ] - [mn2+] [OH-] ² concentration of mnat and [mm 2+] and [OH-] represent OH respectively. flere [Mn2+] = 5.08104 m KSP : [OH-] = 3 part M 2.0X 10-13 5.0 x 10-4 ox1074 = 2.0x105m PH = 14-POH at 25°c) = 14 + log [OH-] = 14+ log (2-0x105) - 9.30 PH equal to 9.30 MACOH)2 will begin to precipitate At