The answers in exercise 5.23 should show that changing the partial pressure changes the instantaneous
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Physical Chemistry
- The combustion of acetylene, C2H2, is a spontaneous reaction given by the equation 2C2H2(g)+5O2(g)4CO2(g)+2H2O(l) As expected for a combustion, the reaction is exothermic. What is the sign of H? What do you expect for the sign of S? Explain the spontaneity of the reaction in terms of the enthalpy and entropy changes.arrow_forwardWhat is the change in entropy, S, for the reaction CaCO3(s)+2H(aq)Ca2+(aq)+H2O(l)+CO2(g) See Table 18.1 for values of standard entropies. Does the entropy of the chemical system increase or decrease as you expect? Explain.arrow_forwardCobalt(II) chloride hexahydrate, CoCl26H2O, is a bright pink compound, but in the presence of very dry air it loses water vapor to the air to produce the light blue anhydrous salt CoCl2. Calculate the standard free-energy change for the reaction at 25C: CoCl26H2O(s)CoCl2(s)+6H2O(g) Here are some thermodynamic data at 25C: What is the partial pressure of water vapor in equilibrium with the anhydrous salt and the hexahydrate at 25C? (Give the value in mmHg.) What is the relative humidity of air that has this partial pressure of water? The relative humidity of a sample of air is Relativehumidity=partialpressureofH2O(g)inairvaporpressureofwater100 What do you expect to happen to the equilibrium partial pressure over the hexahydrate as the temperature is raised? Explain.arrow_forward
- According to a source, lithium peroxide (Li2O2) decomposes to lithium oxide (Li2O) and oxygen gas at about 195C. If the standard enthalpy change for this decomposition is 33.9 kJ/mol, what would you give as an estimate for the standard entropy change for this reaction? Explain.arrow_forwardSomeone once suggested that it is impossible to unscramble a scrambled egg. Describe an unscrambled and a scrambled egg in terms of the concept of entropy.arrow_forwardFor the decomposition of formic acid, HCOOH(l)H2O(l)+CO(g) H = +29 kJ/mol at 25C. a Does the tendency of this reaction to proceed to a state of minimum energy favor the formation of water and carbon monoxide or formic acid? Explain. b Does the tendency of this reaction to proceed to a state of maximum entropy favor the formation of products or reactants? Explainarrow_forward
- Consider the reaction of 2 mol H2(g) at 25C and 1 atm with 1 mol O2(g) at the same temperature and pressure to produce liquid water at these conditions. If this reaction is run in a controlled way to generate work, what is the maximum useful work that can be obtained? How much entropy is produced in this case?arrow_forwardChemists and engineers who design nuclear power plants have to worry about high-temperature reactions because it is possible for water to decompose. (a) Under what conditions does this reaction occur spontaneously? 2H2O(g) 2H2(g) + O2(g) (b) Under conditions where the decomposition of water is spontaneous, do nuclear engineers have to worry about an oxygen/hydrogen explosion? Justify your answer.arrow_forwardWhich contains greater entropy, a quantity of frozen benzene or the same quantity of liquid benzene at the same temperature? Explain in terms of the dispersal of energy in the substance.arrow_forward
- What is the sign of the standard Gibbs free-energy change at low temperatures and at high temperatures for the synthesis of ammonia? 3H2(g) + N2(g) 2NH3(g)arrow_forwardIs the following reaction spontaneous as written? Explain. Do whatever calculation is needed to answer the question. SO2(g)+H2(g)H2S(g)+O2(g)arrow_forward
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