Page 1329 - Chemistry--atom first
P. 1329
Answer Key 1319
73. (a) Rate1 = k[O3]; (b) Rate2 = k[O3][Cl]; (c) Rate3 = k[ClO][O]; (d) Rate2 = k[O3][NO]; (e) Rate3 = k[NO2][O]
75. (a) Doubling [H2] doubles the rate. [H2] must enter the rate equation to the first power. Doubling [NO] increases the rate by a factor of 4. [NO] must enter the rate law to the second power. (b) Rate = k [NO]2[H2]; (c) k = 5.0 103 mol−2 L−2 min−1; (d) 0.0050 mol/L; (e) Step II is the rate-determining step. If step I gives N2O2 in adequate amount, steps 1 and 2 combine to give This reaction corresponds to the observed rate law. Combine steps 1 and 2 with step 3, which occurs by supposition in a rapid fashion, to give the appropriate stoichiometry.
77. The general mode of action for a catalyst is to provide a mechanism by which the reactants can unite more readily by taking a path with a lower reaction energy. The rates of both the forward and the reverse reactions are increased, leading to a faster achievement of equilibrium.
79. (a) Chlorine atoms are a catalyst because they react in the second step but are regenerated in the third step. Thus, they are not used up, which is a characteristic of catalysts. (b) NO is a catalyst for the same reason as in part (a).
80. no changes.
83. The lowering of the transition state energy indicates the effect of a catalyst. (a) B; (b) B 85. The energy needed to go from the initial state to the transition state is (a) 10 kJ; (b) 10 kJ 87. Both have the same activation energy, so they also have the same rate.
Chapter 18
1. The alkali metals all have a single s electron in their outermost shell. In contrast, the alkaline earth metals have a completed s subshell in their outermost shell. In general, the alkali metals react faster and are more reactive than the corresponding alkaline earth metals in the same period.
3.
5. The possible ways of distinguishing between the two include infrared spectroscopy by comparison of known compounds, a flame test that gives the characteristic yellow color for sodium (strontium has a red flame), or
comparison of their solubilities in water. At 20 °C, NaCl dissolves to the extent of compared with
for SrCl2. Heating to 100 °C provides an easy test, since the solubility of NaCl is but that of SrCl2 is Density determination on a solid is sometimes difficult, but there is enough difference (2.165 g/
mL NaCl and 3.052 g/mL SrCl2) that this method would be viable and perhaps the easiest and least expensive test to perform.
7. (a) (b) (c) (d) (e)
9. 11 lb
11. Yes, tin reacts with hydrochloric acid to produce hydrogen gas.
13. In PbCl2, the bonding is ionic, as indicated by its melting point of 501 °C. In PbCl4, the bonding is covalent, as evidenced by it being an unstable liquid at room temperature.
