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chemistry
organic chemistry
Questions and Answers of
Organic Chemistry
The boiling point of benzene is 80.1°C. Estimate: (a) Its molar heat of vaporization and (b) Its vapor pressure at 74°C.
Consider the gas-phase reaction between A2 (green) and B2 (red) to form AB at 298 K:A2(g) + B2(g) ‡Œ 2AB(g) ˆ†G° = - 3.4 kJ/mol(1) Which of the following reaction mixtures is at
Using the data in Appendix 3, calculate the standard entropy changes for the following reactions at 25°C:(a) S(s) + O2(g) → SO2(g)(b) MgCO3(s) → MgO(s) + CO2(g)
Using the data in Appendix 3, calculate the standard entropy changes for the following reactions at 25°C:(a) H2(g) + CuO(s) → Cu(s) + H2O(g)(b) 2Al(s) + 3ZnO(s) → Al2O3(s) + 3Zn(s)(c) CH4(g) +
Without consulting Appendix 3, predict whether the entropy change is positive or negative for each of the following reactions. Give reasons for your predictions.(a) 2KClO4(s) → 2KClO3(s) + O2(g)(b)
State whether the sign of the entropy change expected for each of the following processes will be positive or negative, and explain your predictions.(a) PCl3(l) + Cl2(g) → PCl5(s)(b) 2HgO(s) →
Calculate DG° for the following reactions at 25°C:(a) N2(g) + O2(g) → 2NO(g)(b) H2O(l) → H2O(g)(c) 2C2H2(g) + 5O2(g) → 4CO2(g) + 2H2O(l)
Calculate DG° for the following reactions at 25°C:(a) 2Mg(s) + O2(g) → 2MgO(s)(b) 2SO2(g) + O2(g) → 2SO3(g)(c) 2C2H6(g) + 7O2(g) → 4CO2(g) + 6H2O(l)See Appendix 3 for thermodynamic data.
From the values of ∆H and ∆S, predict which of the following reactions would be spontaneous at 25°C: Reaction A: ∆H 5 10.5 kJ/mol, DS 5 30 J/K ? mol; reaction B: ∆H 5 1.8 kJ/mol, ∆S 5 2113
Find the temperatures at which reactions with the following DH and DS values would become spontaneous: (a) ∆H = - 126 kJ/mol, ∆S = 84 J/K?mol; (b) ∆H = - 11.7 kJ/mol, ∆S 5 2105 J/K ? mol.
Calculate KP for the following reaction at 25°C: H2(g) + I2(g) ⇌ 2HI(g) ∆G° = 2.60 kJ/mol
For the auto ionization of water at 25°C, H2O (l) ΔH+(aq) + OH2(aq) Kw is 1.0 × 10-14. What is ∆G° for the process?
Consider the following reaction at 25°C: Fe(OH)2 ⇌ ΔFe2+(aq) + 2OH-(aq) Calculate ∆G° for the reaction. Ksp for Fe(OH)2 is 1.6 × 10-14.
Calculate DG° and KP for the following equilibrium reaction at 25°C. 2H2O(g) ⇌ Δ2H2(g) + O2(g)
(a) Calculate ∆G° and KP for the following equilibrium reaction at 25°C. The ∆G°f values are 0 for Cl2(g), -286 kJ/mol for PCl3(g), and - 325 kJ/mol for PCl5(g).PCl5(g) ⇌ ΔPCl3(g) +
The equilibrium constant (KP) for the reactionH2(g) + CO2(g) ⇌ H2O(g) + CO(g)is 4.40 at 2000 K. (a) Calculate DG° for the reaction. (b) Calculate DG for the reaction when the partial pressures are
Consider the decomposition of calcium carbonate:CaCO3 ⇌ ΔCaO(s) + CO2(g)Calculate the pressure in atm of CO2 in an equilibrium process (a) at 25°C and (b) at 800°C. Assume that ∆H° 5 177.8
The equilibrium constant KP for the reaction CO(g) + Cl2(g) ⇌ COCl2(g) is 5.62 × 1035 at 25°C. Calculate ∆G°f for COCl2 at 25°C.
At 25°C, DG° for the process H2O(l) ⇌H2O(g) is 8.6 kJ/mol. Calculate the vapor pressure of water at this temperature.
Calculate ∆G° for the process C(diamond) →C(graphite) Is the formation of graphite from diamond favored at 25°C? If so, why is it that diamonds do not become graphite on standing?
Referring to the metabolic process involving glucose on p. 826, calculate the maximum number of moles of ATP that can be synthesized from ADP from the breakdown of one mole of glucose.
In the metabolism of glucose, the first step is the conversion of glucose to glucose 6-phosphate: glucose + H3PO4 → glucose 6-phosphate + H2O ∆G° = 13.4 kJ/mol Because ∆G° is positive, this
A student placed 1 g of each of three compounds A, B, and C in a container and found that after 1 week no change had occurred. Offer some possible explanations for the fact that no reactions took
Use the data in Appendix 3 to calculate the equilibrium constant for the reaction Agl(s) ⇌ Δ Ag+(aq) + I2(aq) at 25°C. Compare your result with the Ksp value in Table 16.2.
Predict the signs of ∆H, ∆S, and ∆G of the system for the following processes at 1 atm: (a) ammonia melts at 260°C, (b) ammonia melts at -77.7°C, (c) ammonia melts at -100°C. (The normal
Consider the following facts: Water freezes spontaneously at 25°C and 1 atm, and ice has a more ordered structure than liquid water. Explain how a spontaneous process can lead to a decrease in
Ammonium nitrate (NH4NO3) dissolves spontaneously and endothermically in water. What can you deduce about the sign of ∆S for the solution process?
Calculate the equilibrium pressure of CO2 due to the decomposition of barium carbonate (BaCO3) at 25°C.
(a) Trouton's rule states that the ratio of the molar heat of vaporization of a liquid (ˆ†Hvap) to its boiling point in kelvins is approximately 90 J/K ? mol. Use the following data to show that
Referring to Problem 18.46, explain why the ratio is considerably smaller than 90 J/K ? mol for liquid HF.
Carbon monoxide (CO) and nitric oxide (NO) are polluting gases contained in automobile exhaust. Under suitable conditions, these gases can be made to react to form nitrogen (N2) and the less harmful
For reactions carried out under standard-state conditions, Equation (18.10) takes the form ˆ†G° = ˆ†H° - Tˆ†S°.(a) Assuming ˆ†H° and ˆ†S° are independent of temperature, derive
How does the entropy of a system change for each of the following processes? (a) A solid melts. (b) A liquid freezes. (c) A liquid boils. (d) A vapor is converted to a solid. (e) A vapor condenses to
The Ksp of AgCl is given in Table 16.2. What is its value at 60°C? [Hint: You need the result of Problem 18.49(a) and the data in Appendix 3 to calculate ∆H°.]
Water gas, a mixture of H2 and CO, is a fuel made by reacting steam with red-hot coke (a by-product of coal distillation): H2O(g) + C(s) ⇌ CO(g) + H2(g) Estimate the temperature at which the
Consider the following Bronstead acid-base reaction at 25°C:HF(aq) + Cl-(aq) ⇌ HCl(aq) + F-(aq)(a) Predict whether K will be greater or smaller than unity. (b) Does DS° or DH° make a greater
Crystallization of sodium acetate from a supersaturated solution occurs spontaneously (see p. 514). What can you deduce about the signs of ∆S and ∆H?
Consider the thermal decomposition of CaCO3: CaCO3(s) ⇌ CaO(s) + CO2(g) The equilibrium vapor pressures of CO2 are 22.6 mmHg at 700°C and 1829 mmHg at 950°C. Calculate the standard enthalpy of
A certain reaction is spontaneous at 72°C. If the enthalpy change for the reaction is 19 kJ/mol, what is the minimum value of ∆S (in J/K ? mol) for the reaction?
Predict whether the entropy change is positive or negative for each of these reactions: (a) Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2(g) (b) O(g) + O(g) → O2(g) (c) NH4NO3(s) → N2O(g) + 2H2O(g) (d)
The reaction NH3(g) + HCl(g) → NH4Cl(s) proceeds spontaneously at 25°C even though there is a decrease in the number of microstates of the system (gases are converted to a solid). Explain.
Use the following data to determine the normal boiling point, in kelvins, of mercury. What assumptions must you make in order to do the calculation? Hg(l): ∆H°i = 0 (by definition) S° = 77.4
Consider the arrangement. Because the volume of the two bulbs is the same, the probability of finding a molecule in either bulb is 1/2. Calculate the probability of all the molecules ending up in the
The molar heat of vaporization of ethanol is 39.3 kJ/mol and the boiling point of ethanol is 78.3°C. Calculate ∆S for the vaporization of 0.50 mol ethanol.
A certain reaction is known to have a ∆G° value of -122 kJ/mol. Will the reaction necessarily occur if the reactants are mixed together?
In the Mond process for the purifi cation of nickel, carbon monoxide is reacted with heated nickel to produce Ni(CO)4, which is a gas and can therefore be separated from solid impurities: Ni(s) +
Calculate DG° and KP for the following processes at 25°C:(a) H2(g) + Br2(l) ⇌ 2HBr(g)(b) 1/2 H2(g) + 12 Br2(l) ⇌ HBr(g)Account for the differences in DG° and KP obtained for (a) and (b).
Calculate the pressure of O2 (in atm) over a sample of NiO at 25°C if ∆G° = 212 kJ/mol for the reaction NiO(s) ⇌ Ni(s) ⇌ 1/2 O2(g)
Comment on the statement: "Just talking about entropy increases its value in the universe."
For a reaction with a negative ∆G° value, which of the following statements is false? (a) The equilibrium constant K is greater than one, (b) the reaction is spontaneous when all the reactants and
Consider the reactionN2(g) + O2(g) ⇌ 2NO(g)Given that ∆G° for the reaction at 25°C is 173.4 kJ/mol, (a) calculate the standard free energy of formation of NO, and (b) calculate KP of the
Heating copper(II) oxide at 400°C does not produce any appreciable amount of Cu:) CuO(s) ⇌ CuO(s) + ½ O2(g) G° = 127.2 kJ/mol However, if this reaction is coupled to the conversion of graphite
The internal engine of a 1200-kg car is designed to run on octane (C8H18), whose enthalpy of combustion is 5510 kJ/mol. If the car is moving up a slope, calculate the maximum height (in meters) to
Consider the decomposition of magnesium carbonate: MgCO3(s) ΔMgO(s) + CO2(g) Calculate the temperature at which the decomposition begins to favor products. Assume that both ∆H° and ∆S° are
(a) Over the years there have been numerous claims about "perpetual motion machines," machines that will produce useful work with no input of energy. Explain why the first law of thermodynamics
The activity series in Section 4.4 shows that reaction(a) is spontaneous while reaction (b) is non spontaneous at 25°C:(a) Fe(s) + 2H+→ Fe2+(aq) + H2(g)(b) Cu(s) + 2H+→ Cu2+(aq) + H2(g)Use the
The rate constant for the elementary reaction 2NO(g) + O2(g) → 2NO2(g) is 7.1 3 109/M2 . s at 25°C. What is the rate constant for the reverse reaction at the same temperature?
The following reaction was described as the cause of sulfur deposits formed at volcanic sites (see p. 780): 2H2S(g) + SO2(g) ⇌ 3S(s) + 2H2O(g) It may also be used to remove SO2 from power plant
Describe two ways that you could measure ∆G° of a reaction.
The following reaction represents the removal of ozone in the stratosphere: 2O3(g) ⇌ 3O2(g) Calculate the equilibrium constant (KP) for the reaction. In view of the magnitude of the equilibrium
A 74.6-g ice cube fl oats in the Arctic Sea. The temperature and pressure of the system and surroundings are at 1 atm and 0°C. Calculate ∆Ssys, ∆Ssurr, and ∆Suniv for the melting of the ice
Comment on the feasibility of extracting copper from its ore chalcocite (Cu2S) by heating: Cu2S(s2 → 2Cu(s) + S(s) Calculate the ∆G° for the overall reaction if the above process is coupled to
Active transport is the process in which a substance is transferred from a region of lower concentration to one of higher concentration. This is a non spontaneous process and must be coupled to a
Large quantities of hydrogen are needed for the synthesis of ammonia. One preparation of hydrogen involves the reaction between carbon monoxide and steam at 300°C in the presence of a copper-zinc
Consider two carboxylic acids (acids that contain the -COOH group): CH3COOH (acetic acid, Ka = 1.8 × 10-5) and CH2ClCOOH (chloroacetic acid, Ka = 1.4 × 10 -3). (a) Calculate ×G° for the
Many hydrocarbons exist as structural isomers, which are compounds that have the same molecular formula but different structures. For example, both butane and isobutane have the same molecular
A rubber band is stretched vertically by attaching a weight to one end and holding the other end by hand. On heating the rubber band with a hot-air blower, it is observed to shrink slightly in
One of the steps in the extraction of iron from its ore (FeO) is the reduction of iron(II) oxide by carbon monoxide at 900°C: FeO(s) + CO(g) ⇌ Fe(s) + CO2(g) If CO is allowed to react with an
Derive the following equation ∆G = RT ln (Q/K) where Q is the reaction quotient and describe how you would use it to predict the spontaneity of a reaction.
The sublimation of carbon dioxide at -78°C is CO2(s) → CO2(g) ∆Hsub = 62.4 kJ/mol Calculate ∆Ssub when 84.8 g of CO2 sublimes at this temperature.
Entropy has sometimes been described as "time's arrow" because it is the property that determines the forward direction of time. Explain.
Referring to Figure 18.1, we see that the probability of finding all 100 molecules in the same bulb is 8 × 10-31. Assuming that the age of the universe is 13 billion years, calculate the time in
A student looked up the ∆G°f, ∆H°f, and S° values for CO2 in Appendix 3. Plugging these values into Equation (18.10), he found that G°f ? ∆H°f ≠ TS° at 298 K. What is wrong with his
For each pair of substances listed here, choose the one having the larger standard entropy value at 25°C. The same molar amount is used in the comparison. Explain the basis for your choice. (a)
Consider the following reaction at 298 K: 2H2(g) + O2(g) → 2H2O(l) ∆H° = 2571.6 kJ/mol Calculate ∆Ssys, ∆Ssurr, and ∆Suniv for the reaction.
As an approximation, we can assume that proteins exist either in the native (or physiologically functioning) state and the denatured state Native ⇌ denatured The standard molar enthalpy and
Which of the following are not state functions: S, H, q, w, T?
Hydrogenation reactions (for example, the process of converting C==C bonds to C--C bonds in food industry) are facilitated by the use of a transition metal catalyst, such as Ni or Pt. The initial
Give a detailed example of each of the following, with an explanation: (a) a thermodynamically spontaneous process; (b) a process that would violate the first law of thermodynamics; (c) a process
At 0 K, the entropy of carbon monoxide crystal is not zero but has a value of 4.2 J/K ? mol, called the residual entropy. According to the third law of thermodynamics, this means that the crystal
Comment on the correctness of the analogy sometimes used to relate a student's dormitory room becoming untidy to an increase in entropy.
The standard enthalpy of formation and the standard entropy of gaseous benzene are 82.93 kJ/mol and 269.2 J/K ? mol, respectively. Calculate ∆H°, ∆S°, and ∆G° for the process at 25°C.
In chemistry, the standard state for a solution is 1 M (see Table 18.2). This means that each solute concentration expressed in molarity is divided by 1 M. In biological systems, however, we define
Balance the following redox equations by the ion electron method:
Given the standard reduction potential for Au3+ in Table 19.1 andAu+(aq) + e- → Au(s) E° 5 1.69 Vanswer the following questions.(a) Why does gold not tarnish in air?(b) Will the following
The ingestion of a very small quantity of mercury is not considered too harmful. Would this statement still hold if the gastric juice in your stomach were mostly nitric acid instead of hydrochloric
When 25.0 mL of a solution containing both Fe2+ and Fe3+ ions is titrated with 23.0 mL of 0.0200 M KMnO4 (in dilute sulfuric acid), all of the Fe2+ ions are oxidized to Fe3+ ions. Next, the solution
When viewed externally, the anode appears negative and the cathode positive (electrons are fl owing from the anode to the cathode). Yet in solution anions are moving toward the anode, which means
Calculate the standard emf of a cell that uses the Mg/Mg2+and Cu/Cu2+ half-cell reactions at 25°C. Write the equation for the cell reaction that occurs under standard-state conditions.
Calculate the standard emf of a cell that uses Ag/Ag+ and Al/Al3+ half-cell reactions. Write the cell reaction that occurs under standard-state conditions.
Predict whether Fe3+ can oxidize I2 to I2 under standard-state conditions.
Which of the following reagents can oxidize H2O to O2(g) under standard-state conditions? H+(aq),Cl-(aq), Cl2(g), Cu2+(aq), Pb2+(aq), MnO4- (aq) (in acid).
Consider the following half-reactions: MnO-4 (aq) + 8H+(aq) + 5e- → Mn2+(aq) + 4H2O(l) NO-3(aq) + 4H+(aq) + 3e- → NO(g) + 2H2O(l) Predict whether NO3- ions will oxidize Mn2+ to MnO4- under
Predict whether the following reactions would occur spontaneously in aqueous solution at 25°C. Assume that the initial concentrations of dissolved species are all 1.0 M.(a) Ca(s) + Cd2+(aq) →
Which species in each pair is a better oxidizing agent under standard-state conditions? (a) Br2 or Au3+. (b) H2 or Ag+. (c) Cd2+ or Cr3+. (d) O2 in acidic media or O2 in basic media.
Which species in each pair is a better reducing agent under standard-state conditions? (a) Na or Li. (b) H2 or I2. (c) Fe2+ or Ag. (d) Br- or Co2+.
Balance the following redox equations by the ion electron method: Discuss.
What is the equilibrium constant for the following reaction at 25°C?
The equilibrium constant for the reactionis 2.69 Ã 1012 at 25°C. Calculate E° for a cell made up of Sr/Sr2+ and Mg/Mg2+ half-cells.
Use the standard reduction potentials to find the equilibrium constant for each of the following reactions at 25°C:(a)(b) (c)
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