matches. Use the References to access important values if needed for this question. Predict whether AS for each reaction would be greater than zero, less than zero, or too close to zero to decide. H₂(g) + Cl₂ (g) 2HCl(g) 2NOBr(g) → 2NO(g) + Br2 (g) CH4 (9) +202(g) → CO₂(g) + 2H₂O(g) CO(g) + 3H₂(g) → CH4 (9) + H₂O(g) 2H₂O2 (1) → 2H₂O(1) + O2(g) Clear All AS > 0 AS < 0 too close to decide

matches. Use the References to access important values if needed for this question. Predict whether AS for each reaction would be greater than zero, less than zero, or too close to zero to decide. H₂(g) + Cl₂ (g) 2HCl(g) 2NOBr(g) → 2NO(g) + Br2 (g) CH4 (9) +202(g) → CO₂(g) + 2H₂O(g) CO(g) + 3H₂(g) → CH4 (9) + H₂O(g) 2H₂O2 (1) → 2H₂O(1) + O2(g) Clear All AS > 0 AS < 0 too close to decide

Chemistry: The Molecular Science

5th Edition

ISBN:9781285199047

Author:John W. Moore, Conrad L. Stanitski

Publisher:John W. Moore, Conrad L. Stanitski

Chapter16: Thermodynamics: Directionality Of Chemical Reactions

Section: Chapter Questions

Problem 29QRT

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Write the balanced chemical equation for the combustion of methane, CH4(g), to give carbon dioxide and water vapor. Explain why it is difficult to predict whether S is positive or negative for this chemical reaction.
Coal is used as a fuel in some electric-generating plants. Coal is a complex material, but for simplicity we may consider it to be a form of carbon. The energy that can be derived from a fuel is sometimes compared with the enthalpy of the combustion reaction: C(s)+O2(g)CO2(g) Calculate the standard enthalpy change for this reaction at 25C. Actually, only a fraction of the heat from this reaction is available to produce electric energy. In electric generating plants, this reaction is used to generate heat for a steam engine, which turns the generator. Basically the steam engine is a type of heat engine in which steam enters the engine at high temperature (Th), work is done, and the steam then exits at a lower temperature (Tl). The maximum fraction, f, of heat available to produce useful energy depends on the difference between these temperatures (expressed in kelvins), f = (Th Tl)/Th. What is the maximum heat energy available for useful work from the combustion of 1.00 mol of C(s) to CO2(g)? (Assume the value of H calculated at 25C for the heat obtained in the generator.) It is possible to consider more efficient ways to obtain useful energy from a fuel. For example, methane can be burned in a fuel cell to generate electricity directly. The maximum useful energy obtained in these cases is the maximum work, which equals the free-energy change. Calculate the standard free-energy change for the combustion of 1.00 mol of C(s) to CO2(g). Compare this value with the maximum obtained with the heat engine described here.
9.83 A student performing a calorimetry experiment combined 100.0 mL of 0.50 M HCl and 100.0 mL of 0.50 M NaOH in a coffee cup calorimeter. Both solutions were initially at 20.0°C, but when the two were mixed, the temperature rose to 23.2°C. (a) Suppose the experiment is repeated in the same calorimeter but this time using 200 mL of 0.50 M HCl and 200.0 mL of 0.50 M NaOH. Will the T observed he greater than, less than, or equal to that in the first experiment, and why? (b) Suppose that the experiment is repeated once again in the same calorimeter, this time using 100 mL of 1.00 M HCl and 100.0 mL of 1.00 M NaOH. Will the T observed he greater than, less than, or equal to that in the first experiment, and why?
The decomposition of ozone, O3, to oxygen, O2, is an exothermic reaction. What is the sign of q? If you were to touch a flask in which ozone is decomposing to oxygen, would you expect the flask to feel warm or cool?
Sodium reacts violently with water according to the equation Na(s) + H2O() NaOH(aq) + H2(g) Without doing calculations, predict the signs of rH and rS for the reaction. Verify your prediction with a calculation.
The reaction between magnesium metal and water (l) produces solid magnesium hydroxide and hydrogen gas. Calculate G for the formation of one mole of Mg(OH)2 at 27C and at 39C.
When calculating rSfromSvalues, it is necessary to look up all substances, including elements in their standard state, such as O2(g), H2(g), and N2(g). When calculating rHfrom rHvalues, however, elements in theirstandard state can be ignored. Why is the situation different forSvalues?
When vapors from hydrochloric acid and aqueous ammonia come in contact, they react, producing a white cloud of solid NH4C1 (Figure 18.9). HCI(g) + NH3(g) NH4Cl(s) Defining the reactants and products as the system under study: (a) Predict whether S(system), S(surroundings), S(universe), rH, and rG (at 298 K) are greater than zero, equal to zero, or less than zero; and explain your prediction. Verify your predictions by calculating values for each of these quantities. (b) Calculate the value of Kp for this reaction at 298 K.
9.20 State the first law of thermodynamics briefly in your own words.
The combustion of methane can be represented as follows: a. Use the information given above to determine the value of H for the combustion of methane to form CO2(g) and 2H2O(l). b. What is Hf for an element in its standard state? Why is this? Use the figure above to support your answer. c. How does H for the reaction CO2(g) + 2H2O (1) CH4(g) + O2(g) compare to that of the combustion of methane? Why is this?
How is the sign of q, heat, defined? How does it relate to the total energy of the system?
When 1.000 g of gaseous butane, C4H10, is burned at 25C and 1.00 atm pressure, H2O(l) and CO2(g) are formed with the evolution of 49.50 kJ of heat. a Calculate the molar enthalpy of formation of butane. (Use enthalpy of formation data for H2O and CO2.) b Gf of butane is 17.2 kJ/mol. What is G for the combustion of 1 mol butane? c From a and b, calculate S for the combustion of 1 mol butane.