Question

5. (36 pts total) To determine the molar solubility and solubility product constant of magnesium carbonate, Matt stirred 5 g of MgCO3 powder in 150 mL of 0.0041 M MgCl2 solution for 15 minutes. After waiting an additional 10 minutes, he separated the undissolved solid by filtration and collected the filtrate in a dry Erlenmeyer flask. He determined the concentration of CO2 in the filtrate to be 1.40 x 10M Answer the following questions based on Matt's experimental data. For problems involving calculations, enter your answer with correct significant figures in the boxes provided. 5.1) (4 pts) What is the total concentration of Mg?' in the filtrate? M 5.2) (4 pts) What is the molar solubility of MgCO3 in 0.0041 M MgCl2? mol/L 5.3) (8 pts) What is the pH of the filtrate, given that the K, of CO2 at 25°C is 1.7 x 10 *? Show all supporting work in the space below. pH = 5.4) (4 pts) What is the Ksp of magnesium carbonate? 5.5) (4 pts) What is the molar solubility of MgCO3 in pure water? 5.6) (8 pts) If Matt used 0.0041 M Na2CO3 as the solvent instead of 0.0041 M MgCl2, how would his experimental results be affected? Circle the correct answers below. a) The total concentration of Mgin the filtrate would ( increase / decrease stay the same ). b) The total concentration of CO32- in the filtrate would ( increase / decrease / stay the same ). c) The molar solubility of MgCO3 would ( increase / decrease / stay the same ). d) The Ksp of magnesium carbonate would increase / decrease / stay the same ). 5.7) (4 pts) After Matt disposes of the filtrate into the appropriate waste container, he notices a white film inside the Erlenmeyer flask. How can Matt best remove this residue? Circle the one correct answer. A. Soak the flask in water overnight. B. Use a scrub brush and glassware detergent. C. Rinse the flask with the 0.0123 M MgCl2 solution D. Rinse the flask with dilute hydrochloric acid. E. Heat the flask using a Bunsen burner.

Answer 1

2992 i astrong electrolyte , it will be present in ponized formed. 1 Mg Ca mg 2+ + au 1 mole mg U₂ - 0.0041 0.0041 0.0082m produces a mole Mar . and a mole ď Mgco, ů a weak electrolyte, it will dissociate partially Also due to presence of of Mg ²+ ( from my cle), its dissocia tion will be suppressed, iet, souebility of my coz it's? in mg cle solution Mg CO₂ (8) ~ Mg 2+ (aq) + CO²- Mg (03 (8) Isto.0041) s Jol) 5.2) concentration 32-) - 5 =1.40 x10-3M 540.4841 total concentration of moet= 5+0.0041 = 1040x10+.4.1x10-3 = 5.5x10-3 M molar soulibility of motor is 0.00410 mg cle T O ES=1040x10 % M Ksp of Mg cos = (8 +0.0041) S = (most][00,?] 0 - 5.5x10-3x 1.40X10 = 7.7x10-6 molle)? let solubility of macos in pure water ist 23 5.4) 5.5) 2 x x mg cosa mga+ (aq) + CO2 (aq) Ksp = [oget] [60,23 peo = 7,7x10-6 =) X= 808x10-3 M sombility = 2.88103 M in pure water

1. 5.3 cosa + H₂O → HCOo + oH to 1040x10²M t= teq (10 40x10²_a) a a. Kur [HCO3J COH) - a? [cą²- ] (1040x103_a) 107x10-4 - a? 1040x10-3_a 2.4x107-667x1024 a = az =) a2+107x10-4 ardouxlo' = 0 a= 4.1810-4 M [OH-] = 401810-4 M POH = - 109 COH) = 3.4 PH = 14 UBOH = 14-364 = 10.6 pH=1006 |