a. Atoms/molecules behave and react differently to each other. Some elements, like the Nobel gases, are less reactive, while other elements like Na and Cl are more reactive. b. What other factors affect the reaction rate of an atom or a molecule? ii. III.

Consider the two space shuttle fuel reactions in Exercises 81 and 82. Which reaction produces more energy per kilogram of reactant mixture (stoichiometric amounts)? 81. The reusable booster rockets of the space shuttle use a mixture of aluminum and ammonium perchlorate as fuel. A possible reaction is 3Al(s)+3NH4ClO4(s)Al2O3(s)+AlCl3(s)+3NO(g)+6H2O(g) Calculate H for this reaction 82. The space shuttle Orbiter utilizes the oxidation of methylhydrazine by dinitrogen tetroxide for propulsion: 4N2H3CH3(l)+5N2O4(l)12H2O(g)+9N2(g)+4CO2(g) Calculate H for this reaction

What is a combustion reaction? Are combustion reactions a unique type of reaction, or are they a special case of a more general type of reaction? Write an equation that illustrates a combustion reaction.

DDT (molar mass = 354.49 g/mol) was a widely used insecticide that was banned from use in the United States in 1973. This ban was brought about due to the persistence of DDT in many different ecosystems, leading to high accumulations of the substance in many birds of prey. The insecticide was shown to cause a thinning of egg shells, pushing many birds toward extinction. If a 20-L drum of DDT was spilled into a pond, resulting in a DDT concentration of 8.75 105 M, how long would it take for the levels of DDT to reach a concentration of 1.41 107 M (a level that is generally assumed safe in mammals)? Assume the decomposition of DDT is a first-order process with a half-life of 56.0 days.

The metals industry was a major source of air pollution years ago. One common process involved roasting metal sulfides in the air 2 PbS(s) + 3 O2(g) 2 PbO(s) + 2 SO2(g) If 2.50 mol of PbS is heated in air, what amount of O2 is required for complete reaction? What amounts of PbO and SO2 are expected?

A 0.20 mol sample of magnesium burns in air to form 0.20 mol of solid MgO. What amount (moles) of oxygen (O2) is required for a complete reaction?

list at least three quantities that must be conserved in chemical reactions.

What is G for the following reaction? 2Br(aq)+Cl2(g)Br2(l)+2Cl(aq) Use data given in Table 19.1.

Polychlorinated biphenyls (PCBs) have been used extensively as dielectric materials in electrical transformers. Because PCBs have been shown to be potentially harmful, analysis for their presence in the environment has become very important. PCBs are manufactured according to the following generic reaction: C12H10+nCl2C12H10nCln.+nHCl This reaction results in a mixture of PCB products. The mixture is analyzed by decomposing the PCBs and then precipitating the resulting Cl asAgCl. a. Develop a general equation that relates the average value of n to the mass of a given mixture of PCBs and the mass of AgCl produced. b. A 0.1947-g sample of a commercial PCB yielded 0.4791 g of AgCl. What is the average value of n for this sample?

Consider the generic chemical equationaA+bBcC+dD (where a, b, c, and d represent coefficients for the chemicals A, B, C, and D, respectively). a. How many possible values are there for “c”? Explain your answer. b. How many possible values are there for “c/d”? Explain your answer.