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chemistry for engineering students

Chemistry For Engineering Students 4th Edition Lawrence S. Brown, Tom Holme - Solutions

Silicon forms a series of compounds analogous to the alkanes and having the general formula SinH2n+2. The first of these compounds is silane, SiH4, which is used in the electronics industry to produce thin ultrapure silicon films. SiH4(g) is somewhat difficult to work with because it is pyrophoric
Explain why ΔGf° of O2(g) is zero.
Using tabulated thermodynamic data, calculate ΔG°for these reactions.(a) Mg3N2(s) + 6 H2O(ℓ) → 2 NH3(g) + 3 Mg(OH)2(s)(b) 4 CH3NH2(g) + 9 O2(g) → 4 CO2(g) + 10 H2O(ℓ) + 2 N2(g)(c) Fe3O4(s) + 4 CO(g) → 3 Fe(s) + 4 CO2(g)(d) P4O10(s) + 6 H2O(ℓ) → 4 H3PO4(aq)
Phosphorus exists in multiple solid phases, including two known as red phosphorus and white phosphorus. (a) Based on their respective heats of formation, which form of phosphorus is defined as the standard state?(b) Now consider the phase transition between white and red phosphorous: P4(s, white)
Calculate ΔG° for the complete combustion of 1 mole of the following fossil fuels: methane (CH4), ethane (C2H6), propane (C3H8), and n-butane (C4H10). Identify any trends that are apparent from these calculations.
Estimate the temperature range over which each of the following reactions is spontaneous.(a) 2 Al(s) + 3 Cl2(g) → 2 AlCl3(s)(b) 2 NOCl(g) → 2 NO(g) + Cl2(g)(c) 4 NO(g) + 6 H2O(g) → 4 NH3(g) + 5 O2(g)(d) 2 PH3(g) → 3 H2(g) + 2 P(g)
Recall that incomplete combustion of fossil fuels occurs when too little oxygen is present and results in the production of carbon monoxide rather than carbon dioxide. Water is the other product in each case.(a) Write balanced chemical equations for the complete and incomplete combustion of
During polymerization, the system usually becomes more ordered as monomers link together. Could an endothermic polymerization reaction ever occur spontaneously? Explain.
If a particular polymerization reaction happened to be endothermic, how could it ever take place? Where would the increase in the entropy of the universe have to arise?
When polymers are recycled, the ends of the long-chain polymer molecules tend to break off, and this process eventually results in a degradation of physical properties, rendering the recycled polymer unusable. Explain why the breaking off of the ends of the polymer molecules is favorable from the
The recycling of polymers represents only one industrial process that allows creating order in one location by creating greater disorder at some other location, often at a power plant. List three other industrial processes that must create disorder in the surroundings to generate the desired
Which one of the following contains both ionic and covalent bonds? (a) BaCO3, (b) MgCl2, (c) BaO,(d) H2S, (e) S O 4 2–
Polymerization reactions are complicated somewhat because they involve very large numbers of molecules. But we can demonstrate the general features of the thermodynamics of polymerization by considering a much smaller model system. Instead of considering the formation of polyethylene, for example,
Use the signs of ΔH and ΔS to explain why ice spontaneously melts at room temperature but not outside on a freezing winter day.Strategy This problem calls for the same type of reasoning used to construct Table 10.2. We must determine whether the process is endothermic or exothermic and whether it
Is the recycling of most plastics primarily a chemical or a physical process? Explain and defend your choice.
List some consumer products made from recycled PET.
Why is recycled PET not more widely used to make new soft drink bottles?
In the thermodynamic definition of a spontaneous process, why is it important that the phrase “continuous intervention” be used rather than just “intervention?”
If the combustion of butane is spontaneous, how can you carry a butane lighter safely in your pocket or purse?
Identify each of the processes listed as spontaneous or nonspontaneous. For each nonspontaneous process, describe the corresponding spontaneous process in the opposite direction.(a) Oxygen molecules dissociate to form oxygen atoms.(b) A tray of water is placed in the sun on a warm day and
Are any of the following exothermic processes not spontaneous under any circumstances?(a) Snow forms from liquid water.(b) Liquid water condenses from water vapor.(c) Fossil fuels burn to form carbon dioxide and water.(d) Monomers react to form a polymer.
Enthalpy changes often help predict whether or not a process will be spontaneous. What type of reaction is more likely to be spontaneous: an exothermic or an endothermic one? Provide two examples that support your assertion and one counterexample.
When a fossil fuel burns, is that fossil fuel the system? Explain your answer.
Murphy’s law is a whimsical rule that says that anything that can go wrong will go wrong. But in an article in the Journal of Chemical Education, Frank Lambert writes, “Murphy’s law is a fraud.” He also writes, “The second law of thermodynamics is time’s arrow, but chemical kinetics is
What observation about the Carnot engine led Carnot to propose the existence of a new state function?
Some games include dice with more than six sides. If you roll two eight-sided dice, with faces numbered one through eight, what is the probability of rolling two eights? What is the most probable roll?
How does probability relate to spontaneity?
Define the concept of a microstate. How is this concept related to the order or disorder of a system?
For each pair of items, tell which has the higher entropy and explain why.(a) Item 1, a sample of solid CO2 at –78°C, or item 2, CO2 vapor at 0°C (b) Item 1, solid sugar, or item 2, the same sugar dissolved in a cup of tea(c) Item 1, a 100-mL sample of pure water and a 100-mL sample of pure
For each process, tell whether the entropy change of the system is positive or negative. (a) A glassblower heats glass (the system) to its softening temperature. (b) A teaspoon of sugar dissolves in a cup of coffee. (The system consists of both sugar and coffee.)(c) Calcium carbonate precipitates
Without doing a calculation, predict whether the entropy change will be positive or negative when each of the following reactions occurs in the direction it is written.(a) CH3OH(ℓ) + 3/2 O2(g) → CO2(g) + 2 H2O(g)(b) Br2(ℓ) + H2(g) → 2 HBr(g)(c) Na(s) + 1/2 F2(g) → NaF(s)(d) CO(g) + 2
An explosion brings down an old building, leaving behind a pile of rubble. Does this cause a thermodynamic entropy increase? If so, where? Write a paragraph explaining your reasoning.
According to Lambert, leaves lying in the yard and playing cards that are in disarray on a table have not undergone an increase in their thermodynamic entropy. Suggest another reason leaves and playing cards may not be a good analogy for the entropy of a system containing, for example, only H2O
A researcher heats a sample of water in a closed vessel until it boils.(a) Does the entropy of the water increase?(b) Has the randomness of the molecules increased? (In other words, are there more physical positions that the molecules can occupy?)(c) What else has increased that affects the entropy
How does the second law of thermodynamics explain a spontaneous change in a system that becomes more ordered when that process is exothermic?
A beaker of water at 40°C (on the left in the drawing) and a beaker of ice water at 0°C are placed side by side in an insulated container. After some time has passed, the temperature of the water in the beaker on the left is 30°C and the temperature of the ice water is still 0°C. Describe what
The molecular scale drawings below represent the three phases of iodine (I2), which is a solid at normal temperature and pressure. (a) In what order should the pictures be placed to put them in terms of decreasing entropy? (b) Assuming the pressure is the same in all three cases, in what order
Diethyl ether is a liquid at normal temperature and pressure, and it boils at 35°C. Given that ΔH is 26.0 kJ/mol for the vaporization of diethyl ether, find its molar entropy change for vaporization.
Calculate the entropy change, ΔS°, for the vaporization of ethanol, C2H5OH, at the boiling point of 78.3°C. The heat of vaporization of the alcohol is 39.3 kJ/mol. C₂H,OH()→ C₂H₂OH(g) ᎪᏛ = ?
Methane can be produced from CO and H2. The process might be done in two steps, as shown below, with each step carried out in a separate reaction vessel within the production plant.You should be able to work this problem without using any additional tabulated data.(a) Calculate ΔH° for reaction
Iodine is not very soluble in water, but it dissolves readily in a solution containing iodide ions by the following reaction:The following graph shows the results of a study of the temperature dependence of ΔG° for this reaction. (The solid line is a best fit to the actual data points.)Notice
Determine whether each of the following statements is true or false. If false, modify to make the statement true.(a) An exothermic reaction is spontaneous.(b) WhenΔ G° is positive, the reaction cannot occur under any conditions.(c) ΔS° is positive for a reaction in which there is an increase in
Polyethylene has a heat capacity of 2.3027 J g-1 °C-1. You need to decide if 1.0 ounce of polyethylene can be used to package a material that will be releasing heat when in use.Consumer safety specifications indicate that the maximum allowable temperature for the polyethylene is 45°C. It can be
A key component in many chemical engineering designs is the separation of mixtures of chemicals.(a) What happens to the entropy of the system when a chemical mixture is separated? (b) Are designs for chemical separation more likely to rely on spontaneous or nonspontaneous processes?
The reaction shown below is involved in the refining of iron. (The table that follows provides all of the thermodynamic data you should need for this problem.)(a) Find ΔH° for the reaction.(b) ΔS° for the reaction above is 557.98 J/K. Find ΔS° for Fe2O3(s).(c) Calculate ΔG° for the reaction
Using only the data given below, determine ΔG° for the following reaction: NO(g) + O(g) → NO₂(g) (Remember that AG is a state function, just like AH.) 2 O3(g) →3 O₂(g) AG= -326 kJ O₂(g) → 2 0(g) AG = 463.6 kJ NO(g) + O₂(g) →→NO₂(g) + O₂(g) AG = -198.3 kJ
The graph below shows ΔG° as a function of temperature for the synthesis of ammonia from nitrogen and hydrogen.(a) Use the graph to estimate ΔS° for the ammonia synthesis reaction.(b) Given that the standard free energy change of formation for ammonia (ΔGf°) is –16.50 kJ/mol, estimate ΔH°
Suppose that you need to know the heat of formation of cyclohexane, C6H12, but the tables you have do not provide the value. You have a sample of the chemical. What could you do to determine the heat of formation?
From a series of hydrocarbons containing only single carbon–carbon bonds, how could you identify a trend for the heat of formation for successive carbon—carbon bond formation?
Thermodynamics provides a way to interpret everyday occurrences. If you live in northern climates, one common experience is that during early winter, snow falls but then melts when it hits the ground. Both the formation and the melting happen spontaneously. How can thermodynamics explain both of
Suppose that you are designing a chemical reactor and you need to know the heat of vaporization for a solvent.You don’t have any thermodynamic tables handy, but you know the boiling point of the liquid and your CAD program can calculate third-law entropies. How would you determine the heat of
Fluorine reacts with liquid water to form gaseous hydrogen fluoride and oxygen.(a) Write a balanced chemical equation for this reaction. (b) Use tabulated data to determine the free energy change for the reaction and comment on its spontaneity. (c) Use tabulated data to calculate the enthalpy
Ammonia can react with oxygen gas to form nitrogen dioxide and water. (a) Write a balanced chemical equation for this reaction. (b) Use tabulated data to determine the free energy change for the reaction and comment on its spontaneity. (c) Use tabulated data to calculate the enthalpy change of
Consider the following thermodynamic data for oxides of manganese.(a) What is the correct chemical nomenclature for each of the first three oxides? (b) Write and balance chemical equations for the conversion of each of these oxides into Mn3O4. (c) Based on the free energy changes of these
(a) When a chemical bond forms, what happens to the entropy of the system? (b) Thermodynamically, what allows any bond formation to occur? (c) What do your answers to parts (a) and (b) suggest must be true about the formation of chemical bonds for the octet rule to hold?
Suppose a particular neodymium-iron-boron magnet contains 1.05% boron. How many significant figures are reported in this value?Strategy Use the general rule for significant figures: Digits reported are significant unless they are zeros whose sole purpose is to position the decimal place.
Visible light is commonly described in terms of its wavelength, which is usually given in units of nanometers. In subsequent calculations, this measurement often needs to be expressed in units of meters. If we are considering orange light of wavelength 615 nm, what is its wavelength in
Replacing fossil fuels with biomass is important for many uses beyond energy production. Compounds derived from biomass may be useful as starting materials for many chemical processes. Nitroanaline had been observed in experiments on biomass from pine needles and can be used as a precursor for
What mass of the unknown compound is formed in the following reactions? (Assume that reactants for which amounts are not given are present in excess.)(a) C2H4 + H2 → C2H6 3.4 g C2H4 reacts to produce x g C2H6(b) CS2 + 3 Cl2 → CCl4 + S2Cl2
Cryolite (Na3AlF6) is used in the commercial production of aluminum from ore. Cryolite itself is produced by the following reaction:A mixture containing 800.0 kg of NaOH, 300.0 kg of Al2O3, and 600.0 kg of HF is heated to 950°C and reacts to completion. What is the maximum mass of Na3AlF6 formed?
A balloon is filled with helium, and its volume is 2.2 L at 298 k. The balloon is then dunked into a thermos bottle containing liquid nitrogen. When the helium in the balloon has cooled to the temperature of the liquid nitrogen (77 K), what will the volume of the balloon be?Strategy We should start
One way to reduce air pollution is to remove potential pollutant gases from an exhaust stream before they are released into the air. Carbon dioxide can be removed from a stream of gas by reacting it with calcium oxide to form calcium carbonate. If we react 5.50 L of CO2 at STP with excess CaO, what
Water has a density that is 13.6 times less than that of mercury. How high would a column of water need to be to measure a pressure of 1 atm?
A cylinder containing 15.0 L of helium gas at a pressure of 165 atm is to be used to fill party balloons. Each balloon must be filled to a volume of 2.0 L at a pressure of 1.1 atm. What is the maximum number of balloons that can be inflated? Assume that the gas in the cylinder is at the same
Calculate the pressure of 15.0 g of methane gas in a 1.50-L vessel at 45.0°C using: (a) The ideal gas law and(b) The van der Waals equation using constants in Table 5.2.Table 5.2 Gas Ammonia, NH3 Argon, Ar Carbon dioxide, CO₂ Helium, He Hydrogen, H₂ Hydrogen fluoride, HF Methane,
A cylinder is filled with toxic COS gas to a pressure of 800.0 torr at 24°C. According to the manufacturer’s specifications, the cylinder may rupture if the pressure exceeds 35 psi (pounds per square inch; 1 atm = 14.7 psi). What is the maximum temperature to which the cylinder could be heated
When a 0.817-g sample of a copper oxide is heated with excess hydrogen gas, a reaction takes place, and 0.187 g of water is formed. What is the apparent formula of the copper oxide?
Carbon can be detected in an X-ray fluorescence experiment by monitoring the emission at a wavelength of 4.47 nm. What is the frequency of this light?Strategy We know that wavelength and frequency are related through Equation 6.1. In using this equation, we will need to be careful of units. Because
Refer to the data and energy-level diagram shown in Problem 6.26, and find the wavelength of light that would be emitted when a hydrogen atom undergoes the transition from the state labeled as n = 4 to the state labeled as n = 2. Express your answer in nm.Data from problem 6.26 n 二 n = 2 n = 1
Using only the periodic table, rank the following elements in order of increasing ionization energy: Br, F, Ga, K, and Se.Strategy We want to arrange the elements from the smallest ionization energy to the largest. Begin by finding each element in the periodic table. Then use the general trends for
Using data from Table 6.5 (page 204), predict the ions that magnesium and aluminum are most likely to form.Table 6.5Strategy Scan the successive ionization energies for each element to find a point were removing one additional electron causes a dramatic increase in the value. It is not likely that
What is the maximum number of electrons in an atom that can have the following quantum numbers?(a) n = 2.(b) n = 3 and ℓ = 1. (c) n = 3, ℓ = 1, and mℓ = 0. (d) n = 3, ℓ = 1, mℓ = −1, and ms = −1/2.
Define the term biocompatibility.
In each of the following pairs of ionic solids, the ions are arranged into similar lattices. Which one has the largest lattice energy?(a) CaO or KF(b) NaF or CsI Strategy Questions like this require us to find some basis for comparison. In this particular case, the factors associated with lattice
List some properties associated with biomaterials used for joint replacements.
Which bond is the most polar: C—H, O—H, or H—Cl? For each of these bonds, determine which atom has a partial positive charge.Strategy Bond polarity depends on the difference in electronegativity between the two bonded atoms. So we can look up the electronegativity values and subtract to find
Describe how PMMA functions as bone cement. How does chemistry play a role in this process?
Chlorofluorocarbons had been used as refrigerants since the 1930s, but their use has largely been phased out worldwide because of concerns about atmospheric ozone depletion. Draw the Lewis structure of dichlorodifluoromethane, CF2Cl2, also known as DuPont’s Freon-12.Strategy Use the algorithm for
The formulas of sodium phosphate and sodium orthosilicate are Na3PO4 and Na4SiO4 respectively. What are the chemical formulas of calcium phosphate and calcium silicate?
Why do biomedical engineers sometimes need to use coatings on certain materials? When coatings are generated, what are the materials used as reactants called?
Use the concept of polarity of water and the basic composition of the body to explain why the polarity of biomaterials is important.
Determine the shape of each of the following species. (a) P O 4 3–, (b) PCl5 Strategy Draw the Lewis structures. Each of these molecules has only single bonds around its central atom. So we can count the number of bonding pairs around the central atom and assign the geometry by consulting
Why is the Na2+ ion not found in nature?
Use VSEPR theory to determine the shape of the NOF molecule.Strategy Once again, we start by drawing the Lewis structure. Then count the number of regions of electron density around the central atom, remembering to count any double or triple bonds as a single region. Determine the spatial
Why do nonmetals tend to form anions rather than cations?
Select the smaller member of each of the following pairs.(a) N and N3–, (b) Ba and Ba2+, (c) Se and Se2–, (d) Co2+ and Co3+
Figure 7.2 depicts the interactions of an ion with its first nearest neighbors, second nearest neighbors, and third nearest neighbors in a lattice.Figure 7.2 (a) Would the interactions with the fourth nearest neighbors be attractive or repulsive?(b) Based on Coulomb’s law, how would the relative
Arrange the following sets of anions in order of increasing ionic radii. (a) Cl–, P3–, S2–, (b) S2–, O2–, Se2–, (c) Br–, N3–, S2–, (d) Br–, Cl–, I–
Which pair will form a compound with the larger lattice energy: Na and F or Mg and F? Why?
Describe the difference between a covalent bond and an ionic bond.
Covalently bonded compounds tend to have much lower melting and boiling points than ionic compounds. How can the differences between ionic and covalent bonding explain this observation?
Considering the potential energy of interacting particles, how does covalent bonding lower the energy of a system?
Coulombic forces are often used to explain ionic bonding. Are coulombic forces involved in covalent bonding as well? Explain.
If the formation of chemical bonds always releases energy, why don’t all elements form dozens of bonds to each atom? In terms of the strengths of the covalent bonds involved, why do combustion reactions release energy?
If the formation of chemical bonds always releases energy, why don’t all elements form dozens of bonds to each atom?
Draw the Lewis dot symbol for each of the following atoms.(a) Boron,(b) Fluorine,(c) Selenium, (d) Indium
Theoretical models for the structure of atomic nuclei predict the existence of superheavy elements that have not yet been discovered and suggest that such elements might be fairly stable if they could be produced. So researchers are currently trying to synthesize these superheavy elements to test
Use Lewis dot symbols to explain why chlorine bonds with only one hydrogen atom.
Define the term lone pair.
How many electrons are shared between two atoms in (a) A single covalent bond, (b) A double covalent bond, and (c) A triple covalent bond?

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