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chemistry
physical chemistry

Questions and Answers of Physical Chemistry

Calculate the entropy of activation for a collision between two structure less particles at 500 K, taking M = 78 g mol-3 and 0'= 0.62 nm2,
The pre-exponential factor for a gas-phase decomposition of ozone at low pressures is 2.3 X 1013 dm-3 mol-1 s-1 and its activation energy is 30.0 k] mol-1. What are? (a) The entropy of activation,
At 25°C, k = 1.55 dm6 mol-2 min-1 at an ionic strength of 0.0241 for a reaction in which the rate-determining step involves the encounter of two singly charged cautions. Use the D cbyc-Huckcl
For a pair of electron donor and acceptor, kc, = 2.02 X 105 S-1for "'-, G" =-0.665 eV. The standard reaction Gibbs energy changes to "'-rG" =-0.975 Ev when a substitute is added to the electron
Refer to Exercise 24.17a. Estimate the value of ke, when r = 1.48 nm.
In the dimerization of methyl radicals at 25°C, the experimental pre-exponential factor is 2.4 x 1010 dm3 ' mol-J s-t. What are?(a) The reactive cross-section,(b) The P factor for the reaction if
The diameter of the methyl radical is about 308 pm. What is the maximum rate constant in the expression d [CzH6J/dt= k [CH3]2 for second order recombination of radicals at room temperature? 10 per
In an experimental study of a bimolecular reaction in aqueous solution, the second-order rate constant was measured at 25°C and at a variety of ionic strengths and the results is tabulated below. It
The total cross-sections for reactions between alkali metal atoms and halogen molecules are given in the table below (R.D. Levine and R.B. Bernstein, Molecular reaction dynamics, Clarendon Press,
For the thermal decomposition Of F2O by the reaction 2 F2O (g) →2 Fl (g) + 0z (g),) Czarnowski and H) Schumacher (Chem. Phys. Lett. 17, 235 (1972)) have suggested the following mechanism:(a) Using
One of the most historically significant studies of chemical reaction rates was that by M. Bodenstein (z. physik. Chem. 29,295 (1899)) of the gas-phase reaction 2 Hl(g) -t H2(g) + I2(g) and its
(a) Distinguish between a step and a terrace. (b) Describe how steps and terraces can be formed by dislocations.
Distinguish between the following adsorption isotherms: Langmuir, BET, Temkin, and Freundlich.
Describe the essential features of the Langmuir-Hinshelwood, Eley-Rideal, and Mars van Krevelen mechanisms for surface-catalyzed reactions.
Discuss the unique physical and chemical properties of zeolites that make them useful heterogeneous catalysts.
Define the terms in and limit the generality of the following expressions: (a) j = jofη, (b) j =joe(1-afη and (c) j = -joe-afη.
Discuss the principles of operation of a fuel cell.
Calculate the frequency of molecular collisions per square centimeter of surface in a vessel containing (a) Nitrogen, (b) Methane at 25°C when the pressure is (i) 10.0 Pa, (ii) 0.150 ~Torr?
Confirm that eqn 24.40 is a solution of eqn 24.39, where [J]t is a solution of the same equation but with k = 0 and for the same initial conditions.
Estimate the orders of magnitude of the partition functions involved in a rate expression. State the order of magnitude of q INA, qR, qV, qE for typical molecules. Check those in the collision of two
The Eyring equation can also be applied to physical processes. As an example, consider the rate of diffusion of an atom stuck to the surface of a solid. Suppose that in order to move from one site to
Show that the intensities of a molecular beam before and after passing through a chamber of length I containing inert scattering atoms are related by 1= Ioe-7{PI, where o is the collision
Show that bimolecular reactions between nonlinear molecules are much slower than between atoms even when the activation energies of both reactions are equal. Use transition state theory and make the
R. Atkinson (J. Phys. Chem. Ref Data 26,215 (1997)) has reviewed a large set of rate constants relevant to the atmospheric chemistry of volatile organic compounds. The recommended rate constant for
The study of conditions that optimize the association of proteins in solution guides the design of protocols for formation of large crystals that are amenable to analysis by the X-ray diffraction
The photosynthetic reaction centre of the purple photosynthetic bacterium Rhodopseudomonas viridis contains a number of bound cofactors that participate in electron transfer reactions. The following
Azurin is a protein containing a copper ion that shuttles between the +2 and +1 oxidation states, and cytochrome c is a protein in which a haem-bound iron ion shuttles between the +3 and +2 oxidation
What pressure of nitrogen gas is required to produce a collision rate of 5.00 x 1019 S-1 at 525 K on a circular surface of diameter 2.0 mm?
Calculate the average rate at which He atoms strike an iron atom in a surface formed by exposing a (l00) plane in metallic iron to helium gas at 100 K and a pressure of24 Pa. Crystals of iron are
A monolayer of CO molecules (effective area 0.165 nm3) is adsorbed on the surface of 1.00 g of an Fe/Al203 catalyst at 77 K, the boiling point of liquid nitrogen. Upon warming, the carbon monoxide
The volume of gas at 20°C and 1.00 bar adsorbed on the surface of 1.50 g of a sample of silica at On C was 1.60 cm-3 at 52.4 kPa and 2.73 cm3 at 104kPa. What is the value of Vmon?
The enthalpy of adsorption of ammonia on a nickel surface is found to be -155 k] mol-1 Estimate the mean lifetime of an NH3 molecule on the surface at 500 K.
The chemisorptions of hydrogen on manganese is activated, but only weakly so. Careful measurements have shown that it precedes 35 per cent faster at 1000 K than at 600 K. What is the activation
The adsorption of a gas is described by the Langmuir isotherm with K = 0.777 kPa-1 at 25°C. Calculate the pressure at which the fractional surface coverage is (a) 0.20, (b) 0.75.
A certain solid sample adsorbs 0.63 mg of CO when the pressure of the gas is 36.0 kPa and the temperature is 300 K. The mass of gas adsorbed when the pressure is 4.0 kPa and the temperature is 300 K
For how long on average would an atom remain on a surface at 400 K if its desertion activation energy were?(a) 20 kO mol-1, (b) 200 k] mol-I? TakeTO = 0.12 ps. For how long on average would the same
A solid in contact with a gas at 8.86 kPa and 25°C adsorbs 4.67 mg of the gas and obeys the Langmuir isotherm. The enthalpy change when 1.00 mmol of the adsorbed gas is desorbed is +12.2 J. What is
Suppose it is known that ozone adsorbs on a particular surface in accord with a Langmuir isotherm. How could you use the pressure dependence of the fractional coverage to distinguish between
Nitrogen gas adsorbed on a surface to the extent of 1.242 cm:' g-I at 350 kPa and 180 K, but at 240 K the same amount of adsorption was achieved only when the pressure was increased to 1.02 MPa. What
In an experiment on the adsorption of ethene on iron it was found that the same volume of the gas was desorbed in 1856 s at 873 K and 8.44 s at 1012 K. What is the activation energy of decoration?
Refer to the preceding exercise. Calculate the magnitude of the electric field at the surface of silica in 4.5 M NaCI (aq) if the surface charge density is 0.12Cm-2.
The transfer coefficient of a certain electrode in contact with M2+and M3+ in aqueous solution at 25°C is 0.42. The current density is found to be 17.0 mA cm when the over voltage is 105 may. What
Determine the exchange current density from the information given in Exercise 25.16b.
Determine the effect that increasing the over potential from 0.50 V to 0.60 V has on the current density in the electrolysis of 1.0 M NaOH (aq), which is 1.22 mA cm-2 at 0.50 V and 25°C. Take a=
Use the data in Table 25.6 for the exchange current density and transfer coefficient for the reaction Fe3++ e"-7 Fe2+on platinum at 25°C to determine what current density would be needed to obtain
Estimate the limiting current density at an electrode in which the concentration of Mg2+ ions is 1.5 mmol dm-3t 25°C. The thickness of the Nernst diffusion layer is 0.32 mm. The ionic conductivity
A 0.10 M FeS04 (aq) solution is electrolyzed between a magnesium cathode and a platinum anode with a current density of 1.50 mA cm-2.The hydrogen over potential is 0.60 V. What will be the
The exchange current density for a PtIFe3+,Fel+ electrode is 2.5 mA cm-I. The standard potential of the electrode is +0.77 V. Calculate the current flowing through an electrode of surface area 1.0
Suppose that the electrode potential is set at 0.50 V. Calculate the current density for the ratio of activities a(Cr3+)la(Cr2+) in the range 0.1 to 10.0 and at 25°C.
What over potential is needed to sustain a current of 15 mA at a Pt] Ce4+'Ce3+ electrode in which both ions are at a mean activity a = 0.01D?
How many electrons or protons are transported through the double layer in each second when the Cu, H21 H+ and Pt ICe4+, Ce3+ electrodes is at equilibrium at 25°C? Take the area as 1.0 ern/ in each
Evaluate the effective resistance at 25°C of an electrode interface for 1.0 c (a) Pb, H2IH+, (b) PtIFe2+, Fe’+ electrodes
State what happens when a platinum electrode in an aqueous solution containing both Fe2+and Ni2+ ions at unit activity is made the cathode of an electrolysis cell.
The over potential for hydrogen evolution on cadmium is about 1 Vat current densities of 1mA cm3. Why may cadmium be deposited from aqueous cadmium sulfate?
The standard potential of the Zn2+/ Zn electrode is -0.76 V at 25°e. The exchange current density for H+ discharge at platinum is 0.79 mA cm-2• Can zinc be plated on to platinum at that
Can iron be deposited on a copper electrode from a unit activity acid solution at 25°C?
Calculate the maximum (zero-current) potential difference of a lead-acid cell, and the maximum possible power output when 100 mA is drawn at 25°e.
The corrosion current density jean at a zinc anode is 2.0 A m. What is the corrosion rate in millimeters per year? Assume uniform corrosion.
The movement of atoms and ions on a surface depends on their ability to leave one position and stick to another, and therefore on the energy changes that occur. As an illustration, consider a
Nickel is face-centred cubic with a unit cell of side 352 pm. What is the number of atoms per square centimeter exposed on a surface formed by(a) (100),(b) (110),(c) (11l) planes? Calculate the
The data for the adsorption of ammonia on barium fluoride are reported below. Confirm that they fit a BET isotherm and find values of C and Vman'
The adsorption of solutes on solids from liquids often follows a Freundlich isotherm. Check the applicability of this isotherm to the following data for the adsorption of acetic acid on charcoal at
A. Akgerman and M. Zardkoohi (J. Chem. Eng. Data 41,185 (1996)) examined the adsorption of phenol from aqueous solution on to fly ash at 20Â°e. They fitted their observations to a Freundlich
M.-G. Olivier and R. Jadot Cl. Chem. Eng. Data 42,230 (1997)) studied the adsorption of butane on silica gel. They report the following amounts of absorption (in moles per kilogram of silica gel) at
In an experiment on the Pt IH,I H+ electrode in dilute H,S04 the following current densities were observed at 25°e. Evaluate ET and jo for the electrode. How would the current density at this
The limiting current density for the reaction I3 + 2e →7 3 r at a platinum electrode is 28.9 μA ern> when the concentration of KI is 6.6 X 10-4 mol dm3 and the temperature 25°e. The diffusion
Consider a cell in which the current is activation -controlled. Show that the current for maximum power can be estimated by plotting 10g (I/Io) and Cl - c21against I (where 10=A2joj~ and Cl and c2
The thickness of the diffuse double layer according to the Guy-Chapman model is given by eqn 19.46. Use this equation to calculate and plot the thickness as a function of concentration and
The redox reactions of quinones have been the subject of many studies over the years and they continue to be of interest to electrochemists. In a study of methane (1,I-dimethyl-3,5-cyclohexanedione)
Although the attractive van der Waals interaction between individual molecules varies as R-6, the interaction of a molecule with a nearby solid (a homogeneous collection of molecules) varies as R-3,
If the dependence of the chemical potential of the gas on the extent of surface coverage is known, the Gibbs adsorption isotherm, eqn 19.50, can be integrated to give a relation between Va and p, as
Show that, for the association part of the surface plasma resonance experiment in Fig. 25.27, R(t) = Req(1 - e-k) and write an expression for kobs' Then, derive an expression for R(t) that applies to
Now suppose that the over potential is in the high over potential region at all times even though it is oscillating. What waveforms will the current across the interface show if it varies linearly
The designers of a new industrial plant wanted to use a catalyst codenamed CR-l in a step involving the fluorination of butadiene. As a first step in the investigation they determined the form of the
The removal or recovery of volatile organic compounds (VOCS) from exhaust gas streams is an important process in environmental engineering. Activated carbon has long been used as an adsorbent in this
The release of petroleum products by leaky underground storage tanks is a serious threat to clean ground water. BTEX compounds (benzene, toluene, ethylbenzene, and xylenes) are of primary concern due
For each group below, determine which metal has a thermodynamic tendency to corrode in moist air at pH = 7. Take as a criterion of corrosion a metal ion concentration of at least 10-6 mol dm-3,
The corrosion potential of iron immersed in a de-aerated acidic solution of pH = 3 is -0.720 V as measured at 25°C relative to the standard calomel electrode with potential 0.2802 V. A Tafel plot of
A sample of chloroform is found to contain 12.0 g of carbon, 106.4 g of chlorine, and 1.01 g of hydrogen. If a second sample of chloroform is found to contain 30.0 g of carbon, what is the total mass
In a reaction, 34.0 g of chromium(III) oxide reacts with 12.1 g of aluminum to produce chromium and aluminum oxide. If 23.3 g of chromium is produced, what mass of aluminum oxide is produced?
The isotope of an unknown element, X, has a mass number of 79. The most stable ion of the isotope has 36 electrons and forms a binary compound with sodium having a formula of Na2X. Which of the
For each of the following ions, indicate the total number of protons and electrons in the ion. For the positive ions in the list, predict the formula of the simplest compound formed between each
Elements in the same family often form oxyanions of the same general formula. The anions are named in a similar fashion. What are the names of the oxyanions of selenium and tellurium: SeO2-, SeO32-,
How would you name HBrO4, KIO3, NaBrO2, and HIO? Refer to Table 2.5 and the acid nomenclature discussion in the text.Table 2.5
Indium oxide contains 4.784 g of indium for every 1.000 g of oxygen. In 1869, when Mendeleev first presented his version of the periodic table, he proposed the formula In2O3 for indium oxide. Before
The designations 1A through 8A used for certain families of the periodic table are helpful for predicting the charges on ions in binary ionic compounds. In these compounds, the metals generally take
A binary ionic compound is known to contain a cation with 51 protons and 48 electrons. The anion contains one third the number of protons as the cation. The number of electrons in the anion is equal
Identify each of the following elements. a. A member of the same family as oxygen whose most stable ion contains 54 electrons b. A member of the alkali metal family whose most stable ion contains 36
A certain element has only two naturally occurring isotopes: one with 18 neutrons and the other with 20 neutrons. The element forms 12 charged ions when in ionic compounds. Predict the identity of
Reaction of 2.0 L of hydrogen gas with 1.0 L of oxygen gas yields 2.0 L of water vapor. All gases are at the same temperature and pressure. Show how these data support the idea that oxygen gas is a
Each of the statements below is true, but Dalton might have had trouble explaining some of them with his atomic theory. Give explanations for the following statements.a. The space filling models for
You take three compounds, each consisting of two elements (X, Y, and/ or Z) and decompose them to their respective elements. To determine the relative masses of X, Y, and Z, you collect and weigh the
Two elements, R and Q, combine to form two binary compounds. In the first compound, 14.0 g of R combines with 3.00 g of Q. In the second compound, 7.00 g of R combines with 4.50 g of Q. Show that
A single molecule has a mass of 7.31 × 10-23 g. Provide an example of a real molecule that can have this mass.
A combustion reaction involves the reaction of a substance with oxygen gas. The complete combustion of any hydrocarbon (binary compound of carbon and hydrogen) produces carbon dioxide and water as
You have two distinct gaseous compounds made from element X and element Y. The mass percents are as follows:Compound I: 30.43% X, 69.57 % YCompound II: 63.64% X, 36.36% YIn their natural standard
You have gone back in time and are working with Dalton on a table of relative masses. Following are his data:0.602 g gas A reacts with 0.295 g gas B0.172 g gas B reacts with 0.401 g gas C0.320 g gas
Explain the law of conservation of mass, the law of definite proportion, and the law of multiple proportions.
A reaction of 1 L of chlorine gas (Cl2) with 5 L of fluorine gas (F2) yields 2 L of a gaseous product. All gas volumes are at the same temperature and pressure. What is the formula of the gaseous
When mixtures of gaseous H2 and gaseous Cl2 react, a product forms that has the same properties regardless of the relative amounts of H2 and Cl2 used. a. How is this result interpreted in terms of

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