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Unformatted text preview: Chemistry 2000 Spring 2006 Test 2 Solutions 1. At the equivalence point, the base has been completely reacted, producing a solution of its conjugate acid. The solution will therefore be acidic, i.e. it will have a p H below 7. Bonus: C H H H N: H H Note the lone pair on the nitrogen atom in the Lewis diagram of methy- lamine. A Lewis base is an electron pair donor. 2. Q = a 2 NO 2 a N 2 O 4 = . 4 2 . 5 = . 32 < K . Since Q < K , the reaction will proceed as written, producing more NO 2 from N 2 O 4 . 3. (a) The equilibrium is Ni ( OH ) 2 ( s ) Ni 2 + ( aq ) + 2OH- ( aq ) . At p H 10, there is more hydroxide in solution, which would tend to push the equilibrium back toward the reactant, i.e. depress the solubil- ity. The solubility would therefore be higher at p H 4. (b) K sp = ( a Ni 2 + )( a OH- ) 2 . a H + = 10- 7 . a OH- = K w a H + = 10- 14 10- 7 = 10- 7 . 1 (Note that its perfectly alright to just remember that a OH- = 10- 7 at p H 7 and 25 C.) a Ni 2 + = K sp a 2 OH- = 6 10- 18 ( 10- 7 ) 2 = 6 10- 4 ....
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