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chemistry for engineering students

Questions and Answers of Chemistry For Engineering Students

Which of the following is more likely to precipitate sulfate ions? PbSO4(s) Pb²+ (aq) + SO4 (aq) 2+ CaSO4(s) Ca²+ (aq) + SO4 (aq) K = 1.8 X 10-8 K = 9.1 x 10-6
Write equilibrium expressions for each of the following heterogeneous equilibria.(a) CaCO3(s) ⇄ Ca2+(aq) + CO3 2–(aq)(b) AgCl(s) ⇄ Ag+(aq) + Cl–(aq)(c) Mg3(PO4)2(s) ⇄ 3 Mg2+(aq) + 2 PO4
The reaction, 3 H2(g) + N2(g) ⇄ 2 NH3(g), has the following equilibrium constants at the temperatures given:(a) At which temperature are reactants favored?(b) At which temperature are products
Write equilibrium expressions for each of the following equilibria.(a) 2 C(s) + O2(g) ⇄ 2 CO(g)(b) Zn2+(aq) + H2S(g) ⇄ ZnS(s) +2 H+(aq)(c) HCl(g) + H2O(ℓ) ⇄ H3O+(aq) + Cl–(aq)(d) H2(g) +
For the equilibria given below, determine each of the following:(a) Equilibrium expressions for K1 and K2 (b) The equation for the reaction that is the sum of the two equations (c) The equilibrium
Using the equationsdetermine the equilibrium constant for the following reaction: HASO4 (aq) AsO4 (aq) + H+ (aq) K₁ = 3.0 X 10-13 HASO4 (aq) + H+ (aq)H₂AsO4 (aq) K₂ = 1.8 x 10²
For each of the following equations, write the equilibrium expression for the reverse reaction.(a) 2 C(s) + O2(g) ⇄ 2 CO(g)(b) AgCl(s) ⇄ Ag+(aq) + Cl–(aq)
(a) In Exercise 12.21, if K1 = 2.1 × 1010 and K2 = 2.3 × 106, what is the value of K3?(b) What is the equilibrium constant, K3′ for the reverse reaction?Data from exercise 12.21For the equilibria
In Exercise 12.24, which reaction has the greater tendency to go to completion as written, reaction 1 or reaction 2?Data from Exercise 12.24Using the equationsdetermine the equilibrium constant for
An engineer is considering the use of bacteria called methanotrophs to remediate the production of small amounts of methane at a mine site. The reaction that takes place can be summarized as CH4(g) +
The following data were collected for the reaction, H2(g)+ I2(g) ⇄ 2 HI(g), at equilibrium at 25°C:[H2] = 0.10 mol L–1, [I2] = 0.20 mol L–1, [HI] = 4.0 mol L–1Calculate the equilibrium
Hydrogen gas and iodine gas react via the following equation:If 0.050 mol HI is placed in an empty 1.0-L flask at 600 K, what are the equilibrium concentrations of HI, I2, and H2? H₂(g) + ₂(g) 2
The following data were collected for a system at equilibrium at 140°C. Calculate the equilibrium constant for the reaction, 3 H2(g) + N2(g) ⇄ 2 NH3(g) at this temperature. [H₂] = 0.10 mol L-¹,
Again the experiment in Exercise 12.33 was redesigned. This time, 0.15 mol each of N2 and O2 was injected into a 5.0-L container at 2500 K, at which the equilibrium constant is 3.6 × 10–3. What
Nitrosyl chloride, NOCl, decomposes to NO and Cl2 at high temperatures:Suppose you place 2.00 mol NOCl in a 1.00-L flask and raise the temperature to 462°C. When equilibrium has been established,
The reaction in Exercise 12.33 was repeated. This time, the reaction began when only NO was injected into the reaction container. If 0.200 mol L–1 NO was injected, what were the equilibrium
The equilibrium constant for the reaction, 3 H2(g) + N2(g) ⇄ 2 NH3(g), at a given temperature is 1.4 × 10–7. Calculate the equilibrium concentration of ammonia, if [H2] = 1.2 × 10–2 mol L–1
A system consisting of 0.100 mole of oxygen gas, O2, is placed in a closed 1.00-L container and is brought to equilibrium at 600 K:What are the equilibrium concentrations of O and O2? O₂(g) 2
The following reaction establishes equilibrium at 2000 K:If the reaction began with 0.100 mol L–1 of N2 and 0.100 mol L–1 of O2, what were the equilibrium concentrations of all species? N₂(g) +
The equilibrium constant of the reaction of Cl2(g) with PCl3(g) to produce PCl5(g) is 51 at a particular temperature. If the initial concentration of PCl3 is 0.012 mol L–1 and the initial
In the reaction in Exercise 12.33, another trial was carried out. The reaction began with an initial concentration of N2 equal to the initial concentration of NO. Each had a concentration of 0.100
The experiment in Exercise 12.33 was redesigned so that the reaction started with 0.15 mol each of N2 and O2 being injected into a 1.0-L container at 2500 k. The equilibrium constant at 2500 K is 3.6
At a particular temperature, the equilibrium constant, K, for the dissociation of N2O4 into NO2 is 133. If the initial concentration of N2O4 is 0.100 mol L–1, what are the concentrations of both
Because carbonic acid undergoes a second ionization, the student in Exercise 12.39 is concerned that the hydrogen ion concentration she calculated is not correct. She looks up the equilibrium
A student is simulating the carbonic acid2hydrogen carbonate equilibrium in a lake:She starts with 0.1000 M carbonic acid. What are the concentrations of all species at equilibrium? H₂CO3(aq) H+
Because calcium carbonate is a sink for CO3 2– in a lake, the student in Exercise 12.39 decides to go a step further and examine the equilibrium between carbonate ion and CaCO3. The reaction
The following reaction is in equilibrium in lake water:Predict the change in the reaction quotient, Q, for each disturbance below and use that prediction to explain how the equilibrium is shifted by
In each of the reactions below, tell how the equilibrium responds to an increase in pressure.(a) CaCO3(s) ⇄ CaO(s) + CO2(g)(b) N2O4(g) ⇄ 2 NO2(g)(c) HCO3 –(aq) + H+(aq) ⇄ H2CO3(aq)
Ammonia is an important starting material for several industrial processes, including the production of fertilizers, polymers, and admixture components for cement. Thus the production of ammonia from
In what geographical region of the country would a civil engineer be most likely to use concrete with air entraining admixtures in a design? Explain your answer.
In Example Problem 12.2, we saw that hydroxide ions precipitate with calcium. Magnesium ions show similar behavior. The two pertinent equilibria are:Which ion is more likely to precipitate hydroxide
What fraction of the annual release of CO2(g) into the atmosphere is the result of concrete production? What is the main chemical step that leads to the production of CO2?
Calcium hydroxide will precipitate from solution by the following equilibrium:Write the equilibrium expression for this reaction.Strategy Write the equilibrium expression as before but do not include
Explain why the hydration process for concrete is exothermic by considering the chemical bonds in the reactants and products.
Concrete used in smokestacks has to be designed to withstand sometimes caustic conditions. Sulfur oxides are produced in some cases, for example, and they would establish equilibrium if they did not
Identify the first chemical step in the production of Portland cement. How is this reaction related to the chemistry that takes place in the carbonation of concrete?
Use the web to look up the rates of reaction for different alkali metals with water. How can you explain the trend in these rates in terms of the concepts presented?
Substances that poison a catalyst pose a major concern for many engineering designs, including those for catalytic converters. One design option is to add materials that react with potential poisons
The following series of pictures represents the progress of a reaction in which A2 molecules dissociate into atoms: A2 → 2 A. Each picture represents a snapshot of the reaction mixture at the
The rate of photodecomposition of the herbicide picloram in aqueous systems was determined by exposure to sunlight for a number of days. One such experiment produced the following results. (Data from
Show that the half-life of a second-order reaction is given by:In what fundamental way does the half-life of a second order reaction differ from that of a first-order reaction? t1/2 1 k[A]o
The production of NO2 from nitrogen and oxygen, N2 + 2 O2 → 2 NO2, was studied in an experiment, and the rate of nitrogen consumption was measured as 2.5 × 10 - 5 mol L-1 s-1. What was the rate
Why is smog appropriately labeled photochemical smog?
In the following rate laws, determine the orders with respect to each substance and the overall order of the reaction.(a) Rate = k[A]2[B], (b) Rate = k[A][B]1/2Strategy The order with respect to
List two types of chemical compounds that must be present in the air for photochemical smog to form. What are the most common sources of these compounds?
Earlier in the chapter we mentioned the decomposition of N2O5:Consider the following data for the kinetics of this reaction:Determine the rate law and rate constant for this reaction at the
What is a VOC? What role do VOCs play in photochemical smog?
In the sort of complex mixture of gases we might find in urban air, many chemical reactions may occur. For example, NO2, which we’ve mentioned as a key species in the formation of ozone, can also
Why do ozone concentrations lag in time relative to other pollutants in photochemical smog?
The photodissociation of NO2 by ultraviolet wavelengths of sunlight initiates the formation of photochemical smog. It is a first-order reaction with a rate constant of 2.95 × 10–3 min–1 at a
A student says nitrogen oxides normally don’t form in the atmosphere because there are not enough collisions between nitrogen and oxygen molecules. What has the student left out of this explanation?
Photodissociation by UV radiation is not the only possible fate of NO2 in urban air. An ordinary decomposition reaction, in which NO2 reacts to form NO and O2, is also possible. This reaction was
Compared to 1990 when the Clean Air Act was last amended, how have the concentrations of criteria pollutants changed?
The rate of the photodissociation of ozone in the example shown in Figure 11.7 may seem slow. But it is actually tremendously faster than what we would see in the absence of ultraviolet light. The
Asphalt is composed of a mixture of organic chemicals. Does an asphalt parking lot contribute directly to the formation of photochemical smog? Explain your answer.
Once ozone forms in photochemical smog, there are a number of reactions by which it is subsequently destroyed. One such reaction occurs when ozone molecules encounter hydroxyl radicals:The following
A newspaper article about air pollution implies that volatile organic compounds are called volatile because they react easily. Write a brief statement that might be appropriate for the comments
The decomposition of N2O5 is given by the equation:The following mechanism is proposed for this reaction:(a) Does this mechanism as written provide the correct stoichiometry? If not, how does it need
In 2015, the EPA set the primary standard for ozone at 0.070 ppm. If a sample of air contains 8 ozone molecules for every 108 molecules of air, does it meet this standard? Explain your answer.
For each of the following, suggest appropriate rate units.(a) Driving from one place to another(b) Drying dishes by hand(c) The beating wings of a mosquito(d) Eyes blinking
For each of the following, suggest an appropriate rate unit.(a) Heart beating (b) Tree growing (c) Automobile wheels rotating (d) Gas evolving in a very fast chemical reaction
Rank the following in order of increasing reaction rate.(a) Dynamite exploding(b) Iron rusting(c) Paper burning
Distinguish between instantaneous rate and average rate. In each of the following situations, is the rate measured the instantaneous rate or the average rate?(a) In a hot dog eating contest, it took
Candle wax is a mixture of hydrocarbons. In the reaction of oxygen with candle wax in Figure 11.2, the rate of consumption of oxygen decreased with time after the flask was covered, and eventually
In the description of the candle in Figure 11.2, we mentioned the consumption of oxygen. Assuming that candle wax is a mixture of hydrocarbons with the general formula CnH2n+2, what other variables
The reaction for the Haber process, the industrial production of ammonia, is:Assume that under certain laboratory conditions ammonia is produced at the rate of 6.29 × 10–5 mol L–1 s–1. At what
Ammonia can react with oxygen to produce nitric oxide and water:If the rate at which ammonia is consumed in a laboratory experiment is 4.23 × 10–4 mol L–1 s–1, at what rate is oxygen consumed?
The following data were obtained in the decomposition of H2O2(aq) to O2(g) and H2O(ℓ). The rate at which oxygen gas was produced was measured. (No oxygen was present initially.)(a) Calculate the
A gas, AB, decomposes and the volume of B2 produced is measured as a function of time. The data obtained are as follows:What is the average rate of production of B2 for the first 8.3 min? For the
Azomethane, CH3NNCH3, is not a stable compound, and once generated, it decomposes. The rate of decomposition was measured by monitoring the partial pressure of azomethane, in torr:Plot the data and
In a method of initial rates experiment, is the measured rate an average rate or an instantaneous rate? Explain.
Second-order rate constants used in modeling atmospheric chemistry are commonly reported in units of cm3 molecule–1 s–1. Convert the following rate constants to L mol–1 s–1:(a) 3.5 × 10–14
For each of the rate laws below, what is the order of the reaction with respect to the hypothetical substances X, Y, and Z? What is the overall order?(a) Rate = k[X][Y][Z], (b) Rate =
The reaction of CO(g) with NO2(g) is second order in NO2 and zero order in CO at temperatures less than 500 k.(a) Write the rate law for the reaction.(b) How will the reaction rate change if the NO2
Show that if the units of rate are mol L–1 s–1, then the units of the rate constant for the following second-order reaction are L mol–1 s–1: H₂(g) + Br₂(g) → 2 HBr rate= k [H₂][Br₂]
One reaction that destroys O3 molecules in the stratosphere is:When this reaction was studied in the laboratory, it was found to be first order with respect to both NO and O3, with a rate constant of
The hypothetical reaction, A + B → C, has the rate law:When [A] is doubled and [B] is held constant, the rate doubles. But the rate increases fourfold when [B] is doubled and [A] is held constant.
The rate of the decomposition of hydrogen peroxide, H2O2, depends on the concentration of iodide ion present. The rate of decomposition was measured at constant temperature and pressure for various
Give the order with respect to each reactant and the overall order for the hypothetical reaction:which obeys the rate law Rate = k[A][B]2. A + B + C D + E
The following experimental data were obtained for the reaction:Determine the reaction order for each reactant and the value of the rate constant. [A] (mol L-¹) 0.127 0.127 0.255 2 A+ 3B C +
The following experimental data were obtained for the reaction of NH4+ and NO2– in acidic solution.Determine the rate law for this reaction and calculate the rate constant. NH4+ (aq) + NO₂ (aq)
Rate data were obtained at 25°C for the following reaction. What is the rate law expression for this reaction? Expt. 1 2 3 4 A + 2B C + 2D Initial [A] (mol L-¹) 0.10 0.30 0.10 0.20 Initial [B] (mol
The reaction:plays a role in the formation of nitrogen dioxide in automobile engines. Suppose that a series of experiments measured the rate of this reaction at 500 K and produced the following
In a heterogeneous system such as wood burning in oxygen, the surface area of the solid can be a factor in the rate of the reaction. Increased surface area of the wood means more collisions with
In wheat-growing areas, such as the plains of the central United States and Canada, harvested wheat is stored in tall grain elevators that are visible for miles in the flat prairie.The wheat is
The decomposition of N2O5 in solution in carbon tetrachloride is a first-order reaction:The rate constant at a given temperature is found to be 5.25 × 10–4 s–1. If the initial concentration of
In Exercise 11.39, if the initial concentration of N2O5 is 0.100 M, how long will it take for the concentration to drop to 0.0100 times its original value?Data from exercise 11.39The decomposition of
For a drug to be effective in treating an illness, its levels in the bloodstream must be maintained for a period of time. One way to measure the level of a drug in the body is to measure its rate of
Amoxicillin is an antibiotic packaged as a powder. When it is used to treat babies and small animals, the pharmacist or veterinarian must suspend it in water, so that it can be administered orally
As with any drug, aspirin (acetylsalicylic acid) must remain in the bloodstream long enough to be effective. Assume that the removal of aspirin from the bloodstream into the urine is a first-order
A possible reaction for the degradation of the pesticide DDT to a less harmful compound was simulated in the laboratory. The reaction was found to be first order, with k = 4.0 × 10–8 s–1 at
The initial concentration of the reactant in a first-order reaction A → products is 0.64 mol/L and the half-life is 30.0 s.(a) Calculate the concentration of the reactant exactly 60 s after
A substance undergoes first-order decomposition. After 40.0 min at 500°C, only 12.5% of the original sample remains. What is the half-life of the decomposition? If the original sample weighed 243 g,
The following data were collected for the decomposition of N2O5:(a) Use appropriate graphs to determine the rate constant for this reaction.(b) Find the half-life of the reaction. Time, t
The rate of decomposition of SO2Cl2 according to the reaction:can be followed by monitoring the total pressure in the reaction vessel. Consider the following data:What must you do to convert these
Peroxyacetyl nitrate (PAN) has the chemical formula C2H3NO5 and is an important lung irritant in photochemical smog. An experiment to determine the decomposition kinetics of PAN gave the data below.
The reaction in which CO2 decomposes to CO and a free radical oxygen atom, O, has an activation energy of 460 kJ mol–1. The frequency factor is 2 × 1011 s–1. What is the rate constant for this
Use the kinetic-molecular theory to explain why an increase in temperature increases reaction rate.
The following rate constants were obtained in an experiment in which the decomposition of gaseous N2O5 was studied as a function of temperature. The products were NO2 and NO3.Determine Ea for this
The table below presents measured rate constants for the reaction of NO with ozone at three temperatures. From these data, determine the activation energy of the reaction in kJ/mol. (Assume the

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