The answers in exercise 5.23 should show that changing the partial pressure changes the instantaneous
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Physical Chemistry
- Silver carbonate, Ag2CO3, is a light yellow compound that decomposes when heated to give silver oxide and carbon dioxide: Ag2CO3(s)Ag2O(s)+CO2(g) A researcher measured the partial pressure of carbon dioxide over a sample of silver carbonate at 220C and found that it was 1.37 atm. Calculate the partial pressure of carbon dioxide at 25C. The standard enthalpies of formation of silver carbonate and silver oxide at 25C are 505.9 kJ/mol and 31.05 kJ/mol, respectively. Make any reasonable assumptions in your calculations. State the assumptions that you make, and note why you think they are reasonable.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_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
- Given the following data at 25C 2NO(g)N2(g)+O2(g)K=1 10 30 2NO(g)+Br2(g)2NOBr(g)K=8 101 Calculate K for the formation of one mole of NOBr from its elements in the gaseous state.arrow_forwardExplain how the entropy of the universe increases when an aluminum metal can is made from aluminum ore. Thefirst step is to extract the ore, which is primarily a formof A12O3, from the ground. After it is purified by freeingit from oxides of silicon and iron, aluminum oxide ischanged to the metal by an input of electrical energy. 2Al2O3(s)electricalenergy4Al(s)+3O2(g)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
- Someone 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_forwardAdenosine triphosphate, ATP, is used as a free-energy source by biological cells. (See the essay on page 624.) ATP hydrolyzes in the presence of enzymes to give ADP: ATP(aq)+H2O(l)ADP(aq)+H2PO4(aq);G=30.5kJ/molat25C Consider a hypothetical biochemical reaction of molecule A to give molecule B: A(aq)B(aq);G=+15.0kJ/molat25C Calculate the ratio [B]/[A] at 25C at equilibrium. Now consider this reaction coupled to the reaction for the hydrolysis of ATP: A(aq)+ATP(aq)+H2O(l)B(aq)+ADP(aq)+H2PO4(aq) If a cell maintains a high ratio of ATP to ADP and H2PO4 by continuously making ATP, the conversion of A to B can be made highly spontaneous. A characteristic value of this ratio is [ATP][ADP][H2PO4]=500 Calculate the ratio [B][A] in this case and compare it with the uncoupled reaction. Compared with the uncoupled reaction, how much larger is this ratio when coupled to the hydrolysis of ATP?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_forward
- Use data given in Tables 6.2 and 18.1 to obtain the value of Kp at 2000C for the reaction N2(g)+O2(g)2NO(g) Nitric oxide is known to form in hot flames in air, which is a mixture of N2 and O2. It is present in auto exhaust from this reaction. Are the data in agreement with this result? Explain.arrow_forwardOn the basis of G for each of the following reactions, decide whether the reaction is spontaneous or non-spontaneous as written. Or, if you expect an equilibrium mixture with significant amounts of both reactants and products, say so. a SO2(g)+2H2S(g)3S(s)+2H2O(g);G=91kJ b 2H2O2(aq)O2(g)+2H2O(l);G=211kJ c HCOOH(l)CO2(g)+H2(g);G=119kJ d I2(s)+Br2(l)2IBr(g);G=7.5kJ e NH4Cl(s)NH3(g)+HCl(g);G=92kJarrow_forwardIf wet silver carbonate is dried in a stream of hot air. the air must have a certain concentration level of carbon dioxide to prevent silver carbonate from decomposing by the reaction Ag2CO3(s)Ag2O(s)+CO2(g) H for this reaction is 79.14 kJ/mol in the temperature range of 25 to 125C. Given that the partial pressure of carbon dioxide in equilibrium with pure solid silver carbonate is 6.23 103 torr at 25C, calculate the partial pressure of CO2 necessary to prevent decomposition ofAg2CO3 at 110C. (Hint: Manipulate the equation in Exercise 79.)arrow_forward
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