6C-hoeger p-exam1[key]

6C-hoeger p-exam1[key] - Midterm 1 KEY (120 points) 1. When...

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Midterm 1 KEY (120 points) 1. When an aqueous solution containing Al 3+ at 25 ° C is mixed with an aqueous solution of hydroxide at 25 ° C an immediate precipitate of insoluble aluminium hydroxide is formed: Al 3+ (aq) + 3 OH (aq) Al(OH) 3 (s) The standard reaction enthalpy ( H )of this reaction is –61.33 kJ/mol. a) ( 5 Pts ) If you were to construct a galvanic cell for the purposes of studying this reaction, what is the standard cell potential ( E ) that you would measure? The appropriate half reactions are: Al(OH) 3 (s) + 3 e Al(s) + 3 OH (aq) E = –2.30 V Al 3+ (aq) + 3 e Al(s) E = –1.68 V You need to sum these two half reactions in such a way as to get the equation given in the beginning of this question. That gives: Al 3+ (aq) + 3 e Al(s) E = –1.68 V Al(s) + 3 OH (aq) Al(OH) 3 (s) + 3 e E = +2.30 V (since you are turning this rxn around) Al 3+ (aq) + 3 OH (aq) Al(OH) 3 (s) E = +0.62 V Self Check: since you were told that “…an immediate precipitate of insoluble aluminium hydroxide
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This note was uploaded on 01/31/2010 for the course CHEM CHEM 6C taught by Professor Hoeger during the Summer '08 term at UCSD.

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6C-hoeger p-exam1[key] - Midterm 1 KEY (120 points) 1. When...

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