Chem 162-2010 homework 9th week

Chem 162-2010 homework 9th week - Chem 162-2010 Hill...

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Chem 162-2010 Hill & Petrucci Chapters 16 & 22 – 9 th Week Homework Chapter 16: Complex Ion Formation 69. A complex ion has Cr 3+ as its central ion and four NH 3 molecules and two Cl - ions as ligands. Write the formula of this complex ion. [Cr(NH 3 ) 4 (Cl) 2 ] + The Solutions Manual has the Cl’s and NH 3 ’s switched in position. It might make a difference. The Solutions Manual might be correct. Don’t worry about that now. We’ll cover it better when we work on Coordination Compounds. 71. Which of the following reagents will increase significantly the concentration of free Zn 2+ ions when it is added to a solution of the complex ion [Zn(NH 3 ) 4 ] 2+ ? Explain. (a) H 2 O(l) (b) NaHSO 4 (aq) (c) NH 3 (aq) (d) HCl (aq) Zn 2+ + 4NH 3 [Zn(NH 3 ) 4 ] 2+ (a) H 2 O No: My guess is the following. H2O will reduce the concentration of all three substances. Since there are five moles of substances on the left, and only one on the right, then according to LeChatelier the reaction will shift to the left. The shift to the left will result in partially bringing the concentrations of the reactants back up to pre-dilution conditions, but not bringing the concentrations of the reactants up to greater than pre-dilution conditions. (b) NaHSO 4 Yes: The acid-forming salt will remove some NH 3 , resulting in a shift of reaction to the left, and a corresponding increase in [Zn 2+ ]. (c) NH 3 No: Addition of NH 3 will result in shifting the reaction to the right, resulting in a lower [Zn 2+ ]. (d) HCl Yes: The acid will remove some NH 3 , resulting in a shift of reaction to the left, and a corresponding increase in [Zn 2+ ]. 73. When a few drops of concentrated Na 2 SO 4 (aq) are added to a dilute solution of AgNO 3 (aq), a white precipitate forms. When a small quantity of concentrated NH 3 (aq) is added to the mixture, the precipitate redissolves, resulting in a colorless solution. When this solution is made acidic with HNO 3 (aq), a white precipitate again appears. Write equations to represent these three observations.
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