Chemical Algebra And Types Of Chemical Reactions
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1
2Example Problems for Chemical equations and stoichiometry – “chemical
algebra” and Types of chemical reactions
1. Much progress has been made on hydrogen fuel cells as a potential replacement for IC engines that contribute to global
warming. Adequate supplies of fuel for the anticipated “hydrogen economy” have not yet been established. Electrolysis
of water to produce H
and O
is very costly in terms of cost of electricity generation. Direct thermal decomposition of
2
2
water into its elements requires temperatures in excess of 2500˚C – too costly also. The catalytic cycle in which sulfur
dioxide reacts with iodine and water to produce sulfuric acid and hydrogen iodide, followed by (1) the decomposition
of hydrogen iodide to its elements at 450˚C and (2) sulfuric acid decomposes to sulfur dioxide, water and oxygen at
850˚C represents a thermal decomposition of water that operates below 900˚C.
(a) Write equations for the three steps of this reaction
(b) Combine the equations for the three steps to obtain the net (overall) reaction
(c) Based on the above, what is the “feedstock” chemical in this catalytic cycle?
(d) Classify each of the above chemical reactions to one of the six categories developed in lecture.
(d) What mass of water is required to produce 1.000 tonne of elemental oxygen by this process?
(Chemistry and Engineering News, September 13, 2004, article starting on p. 31.)
2.
Which compound or compounds in each of the following groups is (are) expected to be soluble in water?
(a) FeO, FeCl
, and FeCO
2
3
(b) AgI, Ag
PO
, and AgNO
3
4
3
(c) NaCl, Li
CO
, and KMnO
2
3
4
3.
Tell whether each of the following is water-soluble or not. If soluble, tell what ions are produced.
(a) BaCl
(b) Cr(NO
)
(c) Pb(NO
)
(d) BaSO
2
3
2
3
2
4
4. Write a balanced equation for the reaction of sulfur trioxide with water.
5.
Balance each of these equations and then classify each one as an acid-base reaction, a precipitation, or a gas-forming reaction. Show
states for the products (s, l, g, aq), and then balance the completed equation. Write the net ionic equation.
(a) MnCl
(aq) + Na
S(aq) → MnS + NaCl
2
2
(b) K
CO
(aq) + ZnCl
(aq) → ZnCO
+ KCl
2
3
2
3
(c) K
CO
(aq) + HClO
(aq) → KClO
+ CO
+ H
O
2
3
4
4
2
2
6.
Classify each of the reactions as an acid-base, precipitation, gas-forming, dissolution, combustion or redox reaction. Show states for
the products (s, l, g, aq), and then balance the completed equation.
Write the net ionic equation.
(a) Fe(OH)
(s) + HNO
(aq) → Fe(NO
)
+ H
O
3
3
3
3
2
(b) FeCO
(s) + HNO
(aq) → Fe(NO
)
+ CO
+ H
O
3
3
3
2
2
2
(c) FeCl
(aq) + (NH
)
S(aq) → FeS + NH
Cl
2
4
2
4
(d) Fe(NO
)
(aq) + Na
CO
(aq) → FeCO
+ NaNO
3
2
2
3
3
3
2+
–
(e) Ba(OH)
(s) → Ba
(aq) + 2 OH
(aq)
2
(f) Mg(s) + O
(g) → MgO(s)
2
(g)
CdCl
(aq) + Na
S(aq) → CdS(s) + NaCl(aq)
2
2
(h) Ca(OH)
(s) + HCl(aq) → CaCl
(aq) + H
O(l)
2
2
2
7.
In each of the following reactions, tell which reactant is oxidized and which is reduced. Designate the oxidizing agent and reducing
agent.
(a) 2 Mg(s) + O
(g) → 2 MgO(s)
2
(b) C
H
(g) + 3 O
(g) → 2 CO
(g) +2 H
O(g)
2
4
2
2
2
(c) Si(s) + 2 Cl
(g) → SiCl
(l)
2
4
8. The final step in the manufacture of platinum metal (for use in automotive catalytic converters and other purposes) is
the reaction:
(s) → 3 Pt(s) + 2 NH
3 (NH
)
PtCl
Cl(s) + 2 N
(g) + 16 HCl(g)
4
2
6
4
2
a) To what classification does this reaction belong?
b) If 12.35 g of (NH
)
PtCl
is heated, what mass of platinum metal, in grams, is expected? What mass of HCl is
4
2
6
obtained as well.
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