General Chemistry Principles, Patterns, and Applications, 2011

c. Ba(CH 3 CO 2 ) 2
d. CaCO 3
2. Of the compounds Sn(CH 3 CO 2 ) 2 and SnS, one is soluble in dilute HCl and the other is soluble only in hot,
concentrated HCl. Which is which? Provide a reasonable explanation.
3. Where in the periodic table do you expect to find elements that form basic oxides? Where do you expect to
find elements that form acidic oxides?
4. Because water can autoionize, it reacts with oxides either as a base (as OH − ) or as an acid (as H 3 O + ). Do you
expect oxides of elements in high oxidation states to be more acidic (reacting with OH − ) or more basic
(reacting with H 3 O + ) than the corresponding oxides in low oxidation states? Why?
5. Given solid samples of CrO, Cr 2 O 3 , and CrO 3 , which would you expect to be the most acidic (reacts most
readily with OH − )? Which would be the most basic (reacts most readily with H 3 O + )? Why?
6. Which of these elements—Be, B, Al, N, Se, In, Tl, Pb—do you expect to form an amphoteric oxide? Why?
N U M E R I C A L PR O BL E M S
1. A 1.0 L solution contains 1.98 M Al(NO 3 ) 3 . What are [OH − ] and [H + ]? What pH is required to precipitate the
cation as Al(OH) 3 ? K sp = 1.3 × 10 −33 and K a = 1.05 × 10 −5 for the hydrated Al 3+ ion.
2. A 1.0 L solution contains 2.03 M CoCl 2 . What is [H + ]? What pH is required to precipitate the cation as
Co(OH) 2 ? K sp = 5.92 × 10 −15 and K a = 1.26 × 10 −9 for the hydrated Co 2+ ion.
3. Given 100 mL of a solution that contains 0.80 mM Ag + and 0.80 mM Cu + , can the two metals be separated by
selective precipitation as the insoluble bromide salts by adding 10 mL of an 8.0 mM solution of
KBr? K sp values are 6.27 × 10 −9 for CuBr and 5.35 × 10 −13 for AgBr. What maximum [Br − ] will separate the ions?
4. Given 100 mL of a solution that is 1.5 mM in Tl + , Zn 2+ , and Ni 2+ , which ions can be separated from solution by
adding 5.0 mL of a 12.0 mM solution of Na 2 C 2 O 4 ?
Precipitate
K sp
Tl2C2O4
2 × 10 −4
ZnC2O4·2H2O 1.38 × 10 −9
NiC2O4
4 × 10 −10
5. How many milliliters of 12.0 mM Na 2 C 2 O 4 should be added to separate Tl + and Zn 2+ from Ni 2+ ?
A N S W E R S
1. [H + ] = 4.56 × 10 −3 ; [OH − ] = 2.19 × 10 −12 ; pH = 2.94
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