A student dissolves 11.4 g of ammonium chloride (NH4C1) in 200. g of water in a well-insulated open cup. She then observes the temperature of the water fall from 22.0 °C to 18.7 °C over the course of 5.7 minutes. Use this data, and any information you need from the ALEKS Data resource, to answer the questions below about this reaction: NH_C1(s) →+ NH (aq) + C1 (aq) You can make any reasonable assumptions about the physical properties of the solution. Be sure answers you calculate using measured data are rounded to the correct number of significant digits. Note for advanced students: it's possible the student did not do the experiment carefully, and the values you calculate may not be the same as the known and published values for this reaction. Is this reaction exothermic, endothermic, or neither? If you said the reaction was exothermic or endothermic, calculate the amount of heat that was released or absorbed by the reaction in this case. Calculate the reaction enthalpy AH per mole of NH₂C1. 0 exothermic endothermic neither KJ kJ mol x10 X

A student dissolves 11.4 g of ammonium chloride (NH4C1) in 200. g of water in a well-insulated open cup. She then observes the temperature of the water fall from 22.0 °C to 18.7 °C over the course of 5.7 minutes. Use this data, and any information you need from the ALEKS Data resource, to answer the questions below about this reaction: NH_C1(s) →+ NH (aq) + C1 (aq) You can make any reasonable assumptions about the physical properties of the solution. Be sure answers you calculate using measured data are rounded to the correct number of significant digits. Note for advanced students: it's possible the student did not do the experiment carefully, and the values you calculate may not be the same as the known and published values for this reaction. Is this reaction exothermic, endothermic, or neither? If you said the reaction was exothermic or endothermic, calculate the amount of heat that was released or absorbed by the reaction in this case. Calculate the reaction enthalpy AH per mole of NH₂C1. 0 exothermic endothermic neither KJ kJ mol x10 X

Chemistry: The Molecular Science

5th Edition

ISBN:9781285199047

Author:John W. Moore, Conrad L. Stanitski

Publisher:John W. Moore, Conrad L. Stanitski

Chapter12: Chemical Equilibrium

Section: Chapter Questions

Problem 84QRT

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Nitromethane, CH3NO2, can be used as a fuel. When the liquid is burned, the (unbalanced) reaction is mainly CH3NO2(l) + O2(g) CO2(g) + N2(g) + H2O(g) a. The standard enthalpy change of reaction (Hvan ) for the balanced reaction (with lowest whole-number coefficients) is 1288.5 kJ. Calculate Hf0 for nitromethane. b. A 15.0-L flask containing a sample of nitromethane is filled with O2 and the flask is heated to 100.C. At this temperature, and after the reaction is complete, the total pressure of all the gases inside the flask is 950. torr. If the mole fraction of nitrogen (nitrogen) is 0.134 after the reaction is complete, what mass of nitrogen was produced?
The formation of aluminum oxide from its elements is highly exothermic. If 2.70 g Al metal is burned in pure O2 to give A12O3, calculate how much thermal energy is evolved in the process (at constant pressure).
The enthalpy of vaporization for water is 40.65 kJ mol-1. As a design engineer for a project in a desert climate, you are exploring the option of using evaporative cooling. (a) If the air has an average volumetric heat capacity of 0.00130 J cm-3 K-1, what is the minimum mass of water that would need to evaporate in order to cool a 5 m? 5 m room with a 3 m ceiling by 5°F using this method? (b) Is this a spontaneous or nonspontaneous process?
For each of the following processes, predict the algebraic sign of rH, rS, and rG. No calculations are necessary; use your common sense. (a) The decomposition of liquid water to give gaseous oxygen and hydrogen, a process that requires a considerable amount of energy. (b) Dynamite is a mixture of nitroglycerin, C3H5N3O9, and diatomaceous earth. The explosive decomposition of nitroglycerin gives gaseous products such as water, CO2, and others; much heat is evolved. (c) The combustion of gasoline in the engine of your car, as exemplified by the combustion of octane. 2 C8H18(g) + 25 O2(g) 16 CO2(g) + 18 H2O(g)
Water gas is produced from the reaction of steam with coal: C(s)+H2O(g)H2(g)+CO(g) Assuming that coal is pure graphite, calculate H for this reaction.
In the reaction of two moles of gaseous hydrogen and one mole of gaseous oxygen to form two moles of gaseous water vapor, two moles of products are formed from three moles of reactants. If this reaction is done at 1.01 104 Pa (and at 0 C), the volume is reduced by 22.4 L. (a) In this reaction, how much work is done on the system (H2, O2, H2O) by the surroundings? (b) The enthalpy change for this reaction is 483.6 kJ. Use this value, along with the answer to (a), to calculate rU, the change in internal energy in the system.
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.
Insoluble PbBr2(s) precipitates when solutions of Pb(NO3)2(aq) and NaBr(aq) are mixed. Pb(NO3)2(aq) + 2 NaBr(aq) PbBr2(s) + 2 NaNO3(aq) rH = ? To measure the enthalpy change, 200. mL. of 0.75 M Pb(NO3)2(aq) and 200. mL of 1.5 M NaBr(aq) are mixed in a coffee-cup calorimeter. The temperature of the mixture rises by 2.44 C. Calculate the enthalpy change for the precipitation of PbBr2(s), in kJ/mol. (Assume the density of the solution is 1.0 g/mL., and its specific heat capacity is 4.2 J/g K.)
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?
A piece of lead of mass 121.6 g was heated by an electrical coil. From the resistance of the coil, the current, and the Time the current flowed, it was calculated that 235 J of heat was added to the lead. The temperature of the lead rose from 20.4C to 35.5C. What is the specific heat of the lead?
Suppose that you are studying kinetic energy of helium molecules: A helium weather balloon rises to an altitude of 40,000 ft; the temperature of the gas drops to 70 F. (a) Make an appropriate choice of system and surroundings and describe it unambiguously. (b) Explain why you chose the system and surroundings you did. (c) Identify transfers of energy and material into and out of the system that would be important for you to monitor in your study.

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