Concept explainers
When a copper wire is exposed to air at room temperature, it becomes coated with a black oxide, CuO. If the wire is heated above a certain temperature, the black oxide is converted to a red oxide, Ct120. At a still higher temperature, the oxide coating disappears. Explain these observations in terms of the
and estimate the temperatures at which the changes occur.
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Chemistry: Principles and Reactions
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- The standard potential, E, for the reaction of Zn(s) and Cl2(g) is +2.12 V. What is the standard free energy change, rG, for the reaction?arrow_forwardThe major industrial use of hydrogen is in the production of ammonia by the Haber process: 3H2(g)+N2(g)2NH3(g) a. Using data from Appendix 4, calculate H, S, and G for the Haber process reaction. b. Is the reaction spontaneous at standard conditions? c. At what temperatures is the reaction spontaneous at standard conditions? Assume H and S do not depend on temperature.arrow_forwardUse the standard free energy of formation data in Appendix G to determine the free energy change for each of the following reactions, which are run under standard state conditions and 25 C. Identify each as either spontaneous or nonspontaneous at these conditions. (a) MnO2(s)Mn(s)+O2(g) (b) H2(g)+Br2(l)2HBr(g) (c) Cu(s)+S(g)CuS(s) (d) 2LiOH(s)+CO2(g)Li2CO3(s)+H2O(g) (e) CH4(g)+O2(g)C(s,graphite)+2H2O(g) (f) CS2(g)+3Cl2(g)CCl4(g)+S2Cl2(g)arrow_forward
- In the late eighteenth century Priestley prepared ammonia by reacting HNO3(g) with hydrogen gas. The thermodynamic equation for the reaction is HNO3(g)+4H2(g)NH3(g)+3H2O(g)H=637kJ (a) Calculate H when one mole of hydrogen gas reacts. (b) What is H when 10.00 g of NH3(g) are made to react with an excess of steam to form HN3(g) and H2 gases?arrow_forwardThe equilibrium constant for a certain reaction increases by a factor of 6.67 when the temperature is increased from 300.0 K to 350.0 K. Calculate the standard change in enthalpy (H) for this reaction (assuming H is temperature-independent).arrow_forward9.72 Although it can be a nuisance when a laptop computer freezes up and needs to be rebooted, we accept that as somewhat inevitable. But clearly the need to occasionally reboot the control system for the power grid would not be acceptable. Use the web to research ways that engineers ensure the reliability of crucial systems like the control infrastructure of the grid, and write a paragraph summarizing the main strategies employed.arrow_forward
- Adenosine 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 incomplete combustion of fossil fuels? Why can this be a problem?arrow_forwardIs the formation of ozone (O3(g)) from oxygen (O2(g)) spontaneous at room temperature under standard state conditions?arrow_forward
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