For the reaction 4HCI(g) + O2(g) 2H,O(g) + 2C1½(g) AH° = -114.4 kJ and AS° = -128.9 J/K The equilibrium constant for this reaction at 276.0 K is Assume that AH° and AS° are independent of temperature.

9.96 Most first aid "cold packs" are based on the endothermic dissolution of ammonium nitrate in water: NH4NO3(s)NH4+(aq)+NO3(aq) H= 25.69 kJ A particular cold pack contains 50.0 g of NH4NO3 and 125.0 g of water. When the pack is squeezed, the NH4NO3dissolves in the water. If the pack and its contents are initially at 24.0°C, what is the lowest temperature that this bag could reach? (Assume that the ammonium nitrate solution has a specific heat of 4.25J g-l K-l, and that the heat capacity of the bag itself is small enough to be neglected.)

The 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).

The free energy change, G, for a process at constant temperature and pressure is related to Suniv and reflects the spontaneity of the process. How is G related to Suniv? When is a process spontaneous? Nonspontaneous? At equilibrium? G is a composite term composed of H, T, and S. What is the G equation? Give the four possible sign combinations for H and S. What temperatures are required for each sign combination to yield a spontaneous process? If G is positive, what does it say about the reverse process? How does the G = H TS equation reduce when at the melting-point temperature of a solid-to-liquid phase change or at the boiling-point temperature of a liquid-to-gas phase change? What is the sign of G for the solid-to-liquid phase change at temperatures above the freezing point? What is the sign of G for the liquid-to-gas phase change at temperatures below the boiling point?

Consider the reaction H2(g)+Br2(g)2HBr(g) where H = 103.8 kJ/mol. In a particular experiment, equal moles of H2(g) at 1.00 atm and Br2(g) at 1.00 atm were mixed in a 1.00-L flask at 25C and allowed to reach equilibrium. Then the molecules of H2 at equilibrium were counted using a very sensitive technique, and 1.10 1013 molecules were found. For this reaction, calculate the values of K, G, and S.

Consider the following reaction at 298 K: 2SO2(g)+O2(g)2SO3(g) An equilibrium mixture contains O2(g) and SO3(g) at partial pressures of 0.50 atm and 2.0 atm, respectively. Using data from Appendix 4, determine the equilibrium partial pressure of SO2 in the mixture. Will this reaction be most favored at a high or a low temperature, assuming standard conditions?

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?

Thermite reactions have been used for welding metal parts such as railway rails and in metal refining. One such thermite reaction is Fe2O3(s)+2Al(s)Al2O3(s)+2Fe(s). Is the reaction spontaneous at room temperature under standard conditions? During the reaction, the surroundings absorb 851.8 kJ/mol of heat.

Consider a metal ion A2+ and its nitrate salt, In an experiment, 35.00 mL of a 0.217 M solution of A(NO3)2 is made to react with 25.00 mL of 0.195 M NaOH. A precipitate, A(OH)2, forms. Along with the precipitation, the temperature increases from 24.8C to 28.2C. What is H for the precipitation of A(OH)2? The following assumptions can be made. • The density of the solution is 1.00 g/mL. • Volumes are additive. • The specific heat of the solution is 4.18 J/g C.

Indicate whether each statement below is true or false. If a statement is false, rewrite it to produce a closely related statement that is true. For a given reaction, the magnitude of the equilibrium constant is independent of temperature. If there is an increase in entropy and a decrease in enthalpy when reactants in their standard states are converted to products in their standard states, the equilibrium constant for the reaction must be negative. The equilibrium constant for the reverse of a reaction is the reciprocal of the equilibrium constant for the reaction itself. For the reaction H2O2(ℓ) ⇌ H2O(ℓ) + O2(g) the equilibrium constant is one half the magnitude of the equilibrium constant for the reaction 2H2O2(ℓ) ⇌ 2H2O(ℓ) + O2(g)