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produce 10 moles of Cl- (aq). The answer is 6/5 = 1.2. However, it is prudent to write and balance
the total reaction:
Br20 (l) + 6 H2O (l) + 5 Cl20 (g) → 2 Br+5O3-(aq) + 12 H+ + 10 Cl- (aq), or
Br2 (l) + 6 H2O (l) + 5 Cl2 (g) → 2 HBrO3 (aq) + 10 HCl (aq). Chemistry 1024b, Winter 2009 Midterm Exam with Solutions Page 8 out of 9 22. Consider the following unbalanced reaction:
FeSO4(aq) + K2Cr2O7(aq) +H2SO4(aq) → Fe2(SO4)3(aq) + Cr2(SO4)3(aq) + K2SO4(aq) + H2O(l). What is the molar ratio of aqueous iron (III) sulfate to aqueous chromium (III) sulfate, according
to the stoichiometry of this reaction?
A) 1.0; B) 1.5; C) 2.0; D) 3.0; E) 6.0
Again, we need to balance the equation first:
Fe+2 (aq) – 1 e → Fe+3 (aq)
(Cr2+6O72-)2- (aq) + 14 H+ (aq) + 6 e → 2 Cr3+ (aq) + 7 H2O (l)
Again, we can have the answer right now, we exchange 6 electrons and produce 6 ions of
Fe+3 (aq) and 2 ions of Cr3+ (aq), which are to form 3 moles of Fe2(SO4)3(aq) and 1 mole of
Cr2(SO4)3(aq), respectively. The answer is, 3/1 = 3.0
The total equation is,
6 FeSO4 (aq) + K2Cr2O7 (aq) + 7 H2SO4 (aq) →
3 Fe2(SO4)3 (aq) + Cr2(SO4)3 (aq) + K2SO4 (aq) + 7 H2O (l)
23. Consider the reaction of industrial ammonia synthesis: N2 (g) + H2 (g) → NH3 (g). This
reaction requires high pressures and temperatures as well as a catalyst. However, even with the
most efficient catalyst, the ammonia yield in one reaction step is only 20.0% of the theoretical
yield. What is the mole fraction of nitrogen gas in the reaction mixture after one reaction step
(i.e., when the reaction was run only once without recirculation)? Assume that initially nitrogen
and hydrogen were taken in stoichiometric proportions, that is, in compliance with the
coefficients of the balanced equation of the reaction. A) 0.111 B) 0.222; C) 0.250; D) 0.000; E) 0.667.
The balanced equation:
N2 (g) + 3 H2 (g) → 2 NH3 (g).
The reaction mixture before one reaction step (assume 1.00 mole of N2 (g)): 1.00 mole of N2 (g);
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This note was uploaded on 02/13/2014 for the course CHEM 1024 taught by Professor Dr.zhifengding during the Winter '12 term at UWO.
- Winter '12