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Chem. 33 2nd Midterm SOLUTION SHEET

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1.(2 point) A mixture contains only NaCl and Fe(NO3)3. A 0.456-g sample of the mixture is dissolved in water, and an excess of NaOH is added, producing a precipitate of Fe(OH)3 by the following reaction: Fe3+(aq) + 3 OH-(aq) → Fe(OH)3(s) The precipitate is filtered, dried, and weighed. Its mass is 0.107 g. Calculate the following: ANSWER: a. b. the mass of iron in the sample the mass of Fe(NO3)3 in the sample a) Fe3+ (aq) + 3 OH-(aq) → Fe(OH)3(s) Fe(OH)3: 55.85 + 3(16.00) + 3(1.008) = 106.87 g/mol 55.85 g Fe 0.107 g Fe(OH) 3 x = 0.0559 g Fe 106.9 g Fe(OH)3 b) Fe(NO3)3: 55.85 + 3(14.01) + 9(16.00) = 241.86 g/mol 241.9 g Fe(NO3 ) 3 0.0559 g Fe x = 0.242 g Fe( NO )3 3 55.85 g Fe