General Chemistry Principles, Patterns, and Applications, 2011

oxidized to H + and O 2 will be reduced to O 2− , but what are the actual products? A reasonable
guess is B 2O 3 and H 2O, both stable compounds.
b. Neither BCl 3 nor water is a powerful oxidant or reductant, so a redox reaction is unlikely;
a hydrolysis reaction is more probable. Nonmetal halides are acidic and react with water
to form a solution of the hydrohalic acid and a nonmetal oxide or hydroxide. In this case,
the most probable boron-containing product is boric acid [B(OH) 3].
c. We normally expect a boron trihalide to behave like a Lewis acid. In this case, however,
the other reactant is elemental hydrogen, which usually acts as a reductant. The iodine
atoms in BI 3 are in the lowest accessible oxidation state (−1), and boron is in the +3
oxidation state. Consequently, we can write a redox reaction in which hydrogen is
oxidized and boron is reduced. Because compounds of boron in lower oxidation states
are rare, we expect that boron will be reduced to elemental boron. The other product of
the reaction must therefore be HI.
Exercise
Predict the products of the reactions and write a balanced chemical equation for each reaction.
a. B 2
H 6
g
a. BBr 3(l) + O 2(g) →
a. B 2
O 3
s
( ) + H 2
O( l) - ® D
( ) + Ca( s) - ® D
( ) + H 2
O( l) - ® D 2B( OH ) 3
( s) + 6H 2 ( g)
Answer: a. B 2
H 6
g
BBr 3(l) + O 2(g) → no reaction a. b. 6B 2
O 3 ( s) + 18Ca s
( ) - ® D B 12 ( s) + 18CaO ( s)
a. Reactions and Compounds of the Heavier Group 13 Elements
All four of the heavier group 13 elements (Al, Ga, In, and Tl) react readily with the halogens to form
compounds with a 1:3 stoichiometry:
Equation 22.10
2M(s) + 3X 2 (s,l,g) → 2MX 3 (s) or M 2 X 6
The reaction of Tl with iodine is an exception: although the product has the stoichiometry TlI3, it
is not thallium(III) iodide, but rather a thallium(I) compound, the Tl + salt of the triiodide ion (I3 − ). This
compound forms because iodine is not a powerful enough oxidant to oxidize thallium to the +3 oxidation
state.
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