QUESTIONS AND PROBLEMS
- How do chemical equations relate to chemical reactions?
- Summarize the information contained in the chemical equation below. How would
this reaction be classified?
CaCl 2 (aq) + Na 2 CO 3 (aq) → CaCO 3 (s) + 2NaCl(aq)
- What are the meanings of (s), (l ), (g), and (aq) after formulas in a chemical equation?
What are the meanings of of ̈ and ←→?
- What is wrong with balancing the chemical equation S + O 2 → SO 3 as S + O 2 →
SO 2?
- From your knowledge of chemistry and chemical formulas write the balanced
equation for heating magnesium carbonate to give magnesium oxide and carbon
dioxide, indicating the physical states of the reactants and products.
- Balance the equation FeSO 4 + H 2 SO 4 + O 2 → Fe 2 (SO 4 ) 3 + H 2 O, which is for a
reaction involved in the formation of pollutant acid mine water.
- Balance each of the following: (a) C 2 H 4 + O 2 → CO 2 + H 2 O, (b) KClO 4 → KClO
- O 2 , (c) FeS + O 2 + H 2 O → FeSO 4 + H 2 SO 4 (d) Fe 2 O 3 + CO → Fe + CO 2 , (e)
H 3 PO 4 + H 2 → PH 3 + H 2 O, (f) P + Cl 2 → PCl 5
- Explain how chemical equations fit in with the general scheme of chemistry as a
language.
- A chemical equation that describes the action of hydrogen sulfide, H 2 S, dissolved in
water is H 2 S ←→ H+ + HS-. What does this equation say and how is it consistent
with the fact that dissolved hydrogen sulfide is a weak acid?.
- From the discussion of reactions of metals with sulfuric acid in Section 4.3 and your
knowledge of the properties of silver jewelry, explain what is likely to happen when
silver metal is placed in sulfuric acid.
- Zinc is a very reactive metal. Explain with chemical equations what you would
expect to happen if zinc metal were placed in sulfuric acid and what would happen
if zinc oxide, ZnO, were placed in sulfuric acid.
- Finely divided steel wool heated red hot and quickly placed into a bottle of oxygen
burns vigorously undergoing the reaction 4Fe + 3O 2 → 2Fe 2 O 3. Why is there no
concern that a steel beam used in construction will burn in air? However, such a
beam can be cut with an oxyacetylene torch by first heating a small portion of it
with the torch, then turning off the acetylene and slowly running the torch across the
beam.
- A water solution of hydrogen peroxide, H 2 O 2 , is relatively stable. But, if a small
quantity of solid manganese oxide is placed in the solution of hydrogen peroxide,
Chap. 4. Chemical Reactions: Making Materials Safely 105
