Chem Question

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Discus: SAT/ACT Tests and Test Preparation: May 2004 Archive: Chem Question
By Onesweetworld87 (Onesweetworld87) on Monday, May 10, 2004 - 06:22 pm: Edit

44. Which of the following solutions has the lowest freezing point?

(A) 0.20 m C6H12O6, glucose
(B) 0.20 m NH4Br
(C) 0.20 m ZnSO4
(D) 0.20 m KMnO4
(E) 0.20 m MgCl2

why is the answer E and not C

By Athlonmj (Athlonmj) on Monday, May 10, 2004 - 06:25 pm: Edit

MgCl2 dissociates into 3 ions while ZnSO4 only dissociates into 2.

By Joeschmoe11 (Joeschmoe11) on Monday, May 10, 2004 - 06:26 pm: Edit

i think cuz MgCl2 ionizes into Mg+ + 2Cl- so it has more ions in the water than ZnS04 which ionizes into Zn2+ and SO42-. So MgCl2 puts out 3 ions while ZnSO4 only puts out 2 ions.

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