Clicker Review - 1 What is the correct name and bonding of...

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Unformatted text preview: 1 What is the correct name and bonding of BF 3 ? 1. boron tri¡uoride, covalent compound 2. boron tri¡uoride, ionic compound 3. boron ¡uoride, covalent compound 4. boron ¡uoride, ionic compound What is the correct name and bonding of BF 3 ? Answer: Covalent molecule since all atoms are nonmetal. Does not contain polyatomic ions. 1 boron atom and 3 ¡uorine atoms, use pre¢xes, except mono of ¢rst element. → Boron tri¡uoride 2 You have a solution of 0.10 M F – and 0.10 M CO 3 2- . You add 0.10 M magnesium nitrate dropwise into the solution. K sp for MgF 2 is 7.4 x 10 –9 and for MgCO 3 is 3.5 x 10 –8 . Which of the following will precipitate ¡rst? 1. magnesium nitrate 2. magnesium carbonate 3. magnesium ¢uoride 4. cannot be determined from the information given 5. none of these You have a solution of 0.10 M F – and 0.10 M CO 3 2- . You add 0.10 M magnesium nitrate dropwise into the solution. K sp for MgF 2 is 7.4 x 10 –9 and for MgCO 3 is 3.5 x 10 –8 . Which of the following will precipitate ¡rst? Answer: K sp (MgF 2 ) = [Mg 2+ ][F- ] 2 7.4 x 10-9 = (x)(2x) 2 → x=1.2 x 10-3 M K sp (MgCO 3 ) = [Mg 2+ ][CO 3 2- ] 3.5 x 10-8 = (x)(x) → x=1.9 x 10-4 M x= [Mg 2+ ]=solubility of Mg salt Smaller x is less soluble - will precipitate ¡rst → MgCO 3 3 A comparision of 1.0 M HOCl and 0.010 M HOCl would be expected to show ____________. 1. that the percent ionization in both solutions is the same 2. that the percent ionization of 1.0 M HOCl is greater than that of 0.010 M HOCl 3. that the percent ionization of 0.010 M HOCl is greater than that of 1.0 M HOCl 4. that a comparison of the percent ionization is not possible for the two solutions A comparision of 1.0 M HOCl and 0.010 M HOCl would be expected to show ____________. Answer: K a is independent of molarity/initial concentration. Less concentrated solution (more dilute) will have higher number of molecules of products to reach K a . Higher number of molecules of products means higher percentage dissociation. 4 Which of the following K a values belongs to the weakest acid? 1. 1.4 x 10-4 2. 1.8 x 10-5 3. 4.0 x 10-4 4. 6.2 x 10-10 5. 6.4 x 10-5 Which of the following K a values belongs to the weakest acid? Answer: Smaller K a means less dissociation → weaker acid. 5 It is desired to prepare a system that functions as a buffer at a pH of 5.6. Of the following systems, the best choice would be ___________________....
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This note was uploaded on 01/19/2012 for the course CHEM 142A taught by Professor Campbell during the Summer '11 term at University of Washington.

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Clicker Review - 1 What is the correct name and bonding of...

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