1. chemsitry

    Calculate the work in kilojoules done during a reaction in which the volume expands from 10.0 L to 95.9 L against an external pressure of 2.5 atm.
  2. Chem

    Part A : This is the first law of thermodynamics question. case 1 - the system expands and the surroundings get hotter case 2 - the system expands and the surroundgins get colder case 3 - the system contracts and the surroundings get hotter case 4 - the
  3. Chemistry

    A gas expands its volume from 4.7 L to 8.9 L at constant temperature. Answer the following: a) If the gas expands against vacuum conditions, calculate the work (in joules) done by the gas. b) Calculate the work done (in joules) by the gas if it expands
  4. chemistry

    A mole of reacts at a constant pressure of 43.0atm via the reaction Before the reaction, the volume of the gaseous mixture was 5.00L . After the reaction, the volume was 2.00L . Calculate the value of the total energy change, , in kilojoules.
  5. chemistry... HELPP

    A gaseous reaction occurs at a constant pressure of 45.0 atm and releases 62.5 Kj of heat. Before the reaction, the volume of the system was 8.60 L . After the reaction, the volume of the system was 3.00 L. Calculate the total internal energy change in
  6. Chemistry

    A gaseous reaction occurs at a constant pressure of 50.0 atm and releases 55.6 kJ of heat. Before the reaction, the volume of the system was 7.60 L. After the reaction, the volume of the system was 2.00 L. Calculate the total internal energy change, Delta
  7. Genera Chemistry

    A certain gas expands in volume from 1.75 L to 8.32 L at constant temperature. Calculate the work done (in Joules) by the gas if it expands against a constant pressure of 3.8 atm. Please explain and show the work and correct answers.
  8. Science

    A certain gas expands in volume from 2.0L to 6.0L at constant temperature. Calculate the work done by the gas if it expands,against a vacuum.
  9. Chemistry

    A gaseous reaction occurs at a constant pressure of 50.0 atm and releases 69.8 kJ of heat. Before the reaction, the volume of the system was 8.80 L . After the reaction, the volume of the system was 2.80 L . Calculate the total internal energy change,
  10. science

    a) calculate the heat of reaction, in kilojoules, for the reaction: 2NO2(g) + 3H2(g)--->2NH3(g) + 2O2(g) b) is the reaction endothermic or exothermic? how can you tell? I will be happy to critique your work on this. You will have to look up the heats of
  11. physics thermodynamics

    A gas expands from a volume of 2.00m^3 to 6.00m^3 and does 6912 joules of work against a constant outside pressure. Calculate this outside pressure in Pa. The answer is 1730 Pa, but I don't know how to get that. I honestly have no idea where to start or
  12. phy

    calculate the work done on the system when 1.00mol of gas held behind a piston expands irreversibly from a volume of 1.00dm cube to a volume of 10.0dm cube against an external pressure of 1.00 bar
  13. Chemistry

    A quantity of 0.020 mole of a gas initially at 0.050 L and 20 degrees Celsius undergoes a constant-temperature expansion until its volume is 0.59 L. Calculate the work done (in joules) by the the gas if it expands (b) pressure of 0.20 atm. (C) If gas in
  14. chemistry

    A quantity of 0.020 mole of a gas initially at 0.050 L and 20 degrees Celsius undergoes a constant-temperature expansion until its volume is 0.59 L. Calculate the work done (in joules) by the the gas if it expands (b) pressure of 0.20 atm. (C) If gas in
  15. ap chemistry

    A sample of gas in a cylinder of volume 4.09 L at 289 K and 3.43 atm expands to 7.73 L by two different pathways. Path A is an isothermal, reversible expansion. Calculate the work
  16. Physics

    Calculate the work done on the system when 1.00 mol of gas held behind a piston expands irriversibly from a volume of 10.0dm^3 against an external pressure of 1.00 bar?
  17. ap chemistry

    A sample of gas in a cylinder of volume 4.2 L at 316 K and 2.68 atm expands to 7.21 L by two different pathways. Path A is an isothermal, reversible expansion. Calculate the work for Path A. Answer in units of J Path B has two steps. In the first step, the
  18. physics

    1. Calculate the work done on the system when 1.00 mol of gas held behind a piston expands irreversibly from volume of 1.00dm cube to a volume 10.00dm cube against an external pressure of 1.00 bar. 2. A perfect gas expand reversibly at a constant
  19. chemistry

    A sample of argon of mass 10.4 g occupies 2100 ml at 30 oC . (i) Calculate the work done by the gas when it expands isothermally against a constant external pressure of 31.1kPa until its volume has increased by 483.1ml. (ii) Calculate the work done by the
  20. Thermochemistry

    Path A A sample of gas in a cylinder of volume 3.96 L at 327 K and 3.28 atm expands to 7.34 L by two different pathways. Path A is an isothermal, reversible expansion. Calculate the work for Path A. Answer in units of J. Path B Path B has two steps. In the
  21. Chemistry

    Part A Calculate the standard enthalpy change for the reaction 2A+B --->2C +2D Use the following data: Substance Delta H(kJ/mol) A -263 B -391 C +203 D -523 Express your answer in kilojoules. MY ANSWER FOR PART A: Delta H =277 kJ PART B----THIS ONE I NEED
  22. Chemistry

    Part A Calculate the standard enthalpy change for the reaction 2A+B --->2C +2D Use the following data: Substance Delta H(kJ/mol) A -263 B -391 C +203 D -523 Express your answer in kilojoules. MY ANSWER FOR PART A: Delta H =277 kJ PART B----THIS ONE I NEED
  23. Chemistry

    A gas expands from 282 mL to 971 mL at constant temperature.Calculate the work done (in joules) by the gas if it expands against a constant pressure of 6.00 atm.
  24. Chemistry

    A sample of gas in a cylinder of volume 3.78 L at 318 K and 3.3 atm expands to 6.76 L by two different pathways. Path A is an isothermal, reversible expansion. Calculate the work for Path A. Answer in units of J
  25. chemistry

    I have to calculate the ΔV= final volume-initial volume For the first trial the final volume was .005mL the initial volume was .03mL, which equaled to -.025mL. The volume was negative because it was exothermic reaction. For the second trial the final
  26. chemistry

    I have to calculate the ΔV= final volume-initial volume For the first trial the final volume was .005mL the initial volume was .03mL, which equaled to -.025mL. The volume was negative because it was exothermic reaction. For the second trial the final
  27. GT

    A GAS EXPANDS IN VOLUME FROM 26.7 ML TO 89.3 ML AT CONSTANTTEMPERATURE. CALCULATE THE WORK DONE (IN JOULES) IF THE GASEXPANDS (A) AGAINST A VACUUM,(B) AGAINST A CONSTANT PRESSUREOF 1.5 ATM, AND (C) AGAINST A CONSTANT PRESSURE OF 2.8 ATM.
  28. chemistry

    1(a) when 25.0ml of 0.500 mol.dm3 H2SO4(AQ) SOLUTION IS added to 0.025dm3 of 1.00 moldm3 KOH SOLUTION , THE TEMPERATURE OF THE REACTION MIXTURE RISES FROM 23.50 CELCIUS TO 30.17 CELCIUS . THE SPECIFIC HEAT CAPACITY AND DENSITY OF WATER 4.20j.g.celcius and
  29. Chemistry

    Consider an ideal gas encloesd in a 1.00 L container at an internal pressure of 10.0 atm. Calculate the work, w, if the gas expands against a constant external pressure of 1.00 atm to a final volume of 20.0 L. w = ____ J now calculate the work done if this
  30. AP Chemistry !

    Can you help me with this? If you can, do it as detail as you can. If not, you can just give me the answer, i'll try to figure how you did it :| A sample of gas in a cylinder of volume 3.96 L at 327 K and 3.28 atm expands to 7.34 L by two different
  31. Chemistry

    A sample of gas occupies a volume of 63.1 mL. As it expands, it does 130.4 J of work on its surroundings at a constant pressure of 783 torr. What is the final volume of the gas? I know that P= 1.03 ATM when converted. I think I'm supposed to use the
  32. chemistry 1B

    A sample of gas occupies a volume of 61.2 mL. As it expands, it does 133.9 J of work on its surroundings at a constant pressure of 783 torr. What is the final volume of the gas.
  33. homework college chem.

    a sample of gas occupies a volume at 73. 1 mL. As it expands, it does 135.0 J of work on its surroundings at a constant pressure of 783 torr. what is the final volume of gas?
  34. Chemistry

    Consider an ideal gas encloesd in a 1.00 L container at an internal pressure of 10.0 atm. Calculate the work, w, if the gas expands against a constant external pressure of 1.00 atm to a final volume of 20.0 L. w = ____ J now calculate the work done if this
  35. chemisty

    A cylinder with a moving piston expands from an initial volume of 0.350L against an external pressure of 2.70atm . The expansion does 251J of work on the surroundings. What is the final volume of the cylinder?
  36. Physics

    the volume of a monoatomic ideal gas doubles in an adiabatic expansion. by considering 135 moles of gas with an initial pressure of 330kPa and an initial volume of 1.2m^3, the gas is then expands adiabatically to a volume of 2.4m^3. FIND THE WORK DONE BY
  37. chemistry

    1. the volume of an idea gas is 2.06L at standard temperature and pressure. Calculate the volume at 1.75 atm and 27CELCIUS. 2. Ethane, C2h6 has a molar heat of vaporization of 15kj/mole. How many kilojoules or energy are required to vaporize 5 g of ethane?
  38. physics

    One mole of an ideal gas does 3400 J of work on its surroundings as it expands isothermally to a final pressure of 1.00 atm and volume of 22.0 L. (a) Determine the initial volume in m^3. i tried using the formula w=integral f/i pdv 3400J=
  39. physics

    One mole of an ideal gas does 3400 J of work on its surroundings as it expands isothermally to a final pressure of 1.00 atm and volume of 22.0 L. (a) Determine the initial volume in m^3. i tried using the formula w=integral f/i pdv 3400J=
  40. chemistry

    CH3OH(g) ----> CO(g) + 2H2 (g) (delta H =+90.7k) A) is heat absorbed or released in the course of this reaction? b) calculate the amount of heat transferred when 45.0g of CH3OH(g)is decomposed by this reaction at constant pressure. c) for a given sample of
  41. ap chem

    Assuming the volumes of all gases in the reaction are measured at the same temperature and pressure, calculate the volume of water vapor obtainable by the explosive reaction of a mixture of 725mL of hydrogen gas and 325mL of oxygen gas. andd... Calculate
  42. Physics..

    A container of gas is at a pressure of 1.3x10^5 Pa and a volume of 6.0m^3. How much work is done by the gas if it expands at constant pressure to twice its initial volume? Please help me I really don't know what to do,,,
  43. Physics

    A gram molecule of a gas at 127°C expands isothermally until its volume is doubled. Find the amount of work done and heat absorbed.
  44. college of cape town

    A gas at 273 kelvin expands by 0,1 cubic metre if it is heated through 50kelvin. Calculate the original volume at constant pressure.
  45. Physics

    A container of gas is at a pressure of 1.3x10^5 Pa and a volume of 6.0m^3. How much work is done by the gas if it expands at constant pressure to twice its initial volume? Please help ;_;
  46. Chemistry

    A sample of gas in a cylinder of volume 3.64 L at 275 K and 2.68 atm expands to 7.04 L by two different pathways. Path A is an isothermal, reversible expansion. Calculate the work for Path A. Answer in units of J What I did was basically W=-P(delta V)
  47. chemistry

    A 100 w lightbulb is place in a cylinder equipped with a moveable piston. The ligshtbulb is turned on for 0.015 hours, and the assembly expands from initial volume of 0.85 L to a final volume of 5.88 L against an external pressure of 1.0 atm. Use the
  48. AP Chemistry

    1) Calculate the volume of air at 30 degrees C and 1.00 atm that is needed to burn completely 10.0 grams of propane. Assume that air is 21.0 percent O2 by volume. 2) Assuming all of the heat evolved in burning 30.0 g of propane is transferred to 8.00 kg of
  49. physics

    Hi!could anyone help me please, Thank. Gas in a container is at a pressure of 1.3 atm and a volume of 1.0 m3. (a) What is the work done on the gas if it expands at constant pressure to twice its initial volume? (b) What is the work done on the gas if it is
  50. physics

    Hi, could anyone help me please, Thank. Gas in a container is at a pressure of 1.3 atm and a volume of 1.0 m3. (a) What is the work done on the gas if it expands at constant pressure to twice its initial volume? (b) What is the work done on the gas if it
  51. Chemistry

    Calculate the work done (in joules) by a chemical reaction if the volume increases from 3.3L to 3.5L against a constant external pressure of 3.7atm .
  52. Calculus 2

    The pressure P of a gas is related to its volume V by the formula P=k/V where k is a constant. A quantity of gas with an initial volume of 1 cubic meter and a pressure of 2.5 newtons per square meter expands to a volume of 16 cubic meters. Find the work
  53. Chemistry

    I had to perform an experiment for rate of reaction. I have to calculate the concentration of Na2S2O3 in the reaction solutions based on the volume used in each reaction flask and the total volume calculated. There were five flasks used and for all 5 of
  54. Chemistry

    1. How much heat in kilojoules is needed to bring 2.00 kg of water from 27.7 to 82.6 ¡ãC (comparable to making four cups of coffee)? 2. Consider the reaction: CH4(g) + 2O2(g) ¡ú CO2(g) + 2H2O(g) Use data in table below Compound S¡ã, J¡¤mol-1¡¤K-1
  55. physics

    can anyone show me how to do this? A container of gas is at a pressure of 3.7 * 10^5 Pa. how much work is done by the gas if its volume expands by 1.6 m^3? thanks
  56. CHEMISTRY

    Mass (before reaction): test tube + HCl(aq) + stir bar + capsule 26.600 g Mass (after reaction): test tube + HCl(aq) + stir bar + capsule 25.300 g Volume of water displaced from the squirt bottle 148 mL Temperature of the CO2(g) 287.4 K Pressure (atm)
  57. chem

    the work done by a gas when it expands to 96 L is 4100 J. if the external pressure is 2.0 atm, determine the initial volume of the gas.
  58. Chem

    A 1.00-mole sample of ammonia at 13.0 bar and 20°C in a cylinder fitted with a movable piston expands against a constant external pressure of 1.00 bar. At equilibrium, the pressure and volume of the gas are 1.00 bar and 22.0 L, respectively. a) calculate
  59. Biochemistry

    You wish to make 3 reactions (1 ml each) with the specified amounts of protein. The remainder of each reaction consists entirely of buffer. The source of your protein is a stock solution that has a concentration of 0.5 mg/ml. What is the volume of stock
  60. Chemistry

    How much heat (in kilojoules) is released on reaction of 4.10 g of Al? Reaction: 2Al(s) + 3Cl2(g)--->2AlCl3(s) Delta H= -1408.4 KJ
  61. Chemistry 121

    . Using your calculated value for molar heat of reaction, how much heat would be given off in kilojoules if 3.0 grams of magnesium were to react with excess hydrochloric acid. Show work for your calculation. Value is 31.304 kJ/mol Mg
  62. chemistry

    A 7.56-g sample of gas is in a balloon that has a volume of 10.5 L. Under an external pressure of 1.05 atm, the balloon expands to a volume of 15.00 L. Then the gas is heated from 0.00 degree C to 25 C. If the specific heat of the gas is 0.909 J/g*C, what
  63. General Chemistry I

    A sample of gas occupies a volume of 59.9 mL. As it expands, it does 126.2 J of work on its surroundings at a constant pressure of 798 torr. What is the final volume of the gas? a. 61.1 mL b. 1,250 mL c. 218 mL d. 1,490 mL e. None of the above I used the
  64. physics

    A gas at 273 kelvin expands by 0.1 cubic metre if it is heated through 50 kelvin. Calculate the original volume at constant pressure
  65. Physics

    Pt. 1 Gas in a container is at a pressure of 2.3 atm and a volume of 6.1 m3. What is the work done on the gas if it expands at constant pressure to five times its initial volume? Answer in units of J My wrong answer: 56.12 Pt. 2: What is the work done on
  66. Physics

    Pt. 1 Gas in a container is at a pressure of 2.3 atm and a volume of 6.1 m3. What is the work done on the gas if it expands at constant pressure to five times its initial volume? Answer in units of J My wrong answer: 56.12 Pt. 2: What is the work done on
  67. chemistry

    Calculate ∆T for the reaction. Assume the initial temperature of both reactants is 25.0◦C. Calculate the volume of the reaction mixture. Calculate the mass of the reaction mixture. Assume the density of the mixture is 1.03 g mL^(-1). Calculate the heat
  68. Chemistry

    A sample of carbon monoxide gas whose mass is 6.37 g is heated from 25 oC to 192 oC at a constant pressure of 4.12 bar. Calculate q (in J) for this process. I got an answer of ~1110J Calculate w (in J) for this process. I am unsure how to calculate work
  69. physics

    2. Rod A, which is 30 cm long, expands by 0.045 cm when heated from 0°C to 100°C. Rod B, also 30 cm long expands by 0.075 cm for the same change in temperature. A third Rod C, also 30 cm long is made up of the materials of rod A and B, connected end to
  70. chem

    If an ideal gas is allowed to expand into a vacuum, this means that the external pressure is 0. This doesn't affect the internal pressure though, correct? For example: I have a problem in which one mole of an ideal gas at 300. K and at a volume of 10.0 L
  71. chemistry

    Consider the following reaction: 2HBr(g)---> H_2(g) + Br_2(g) B)In the first 15.0s of this reaction, the concentration of HBr dropped from 0.510M to 0.455M. Calculate the average rate of the reaction in this time interval. C)If the volume of the reaction
  72. CHEMISTRY

    Calculate the maximum work done when two moles of N2 expands isothermally from 10 litres to 20 litres at 25o C
  73. Chemistry HELP!!!!

    Nitric oxide (NO) reacts with molecular oxygen as follows: 2NO(g) + O2(g) ¨ 2NO2(g) Initially NO and O2 are separated as shown below. When the valve is opened, the reaction quickly goes to completion. Determine what gases remain at the end of the
  74. Chemistry

    Nitric oxide (NO) reacts with molecular oxygen as follows: 2NO(g) + O2(g) ¨ 2NO2(g) Initially NO and O2 are separated as shown below. When the valve is opened, the reaction quickly goes to completion. Determine what gases remain at the end of the
  75. Science

    Consider the following reaction: 2Na + Cl2  2NaCl ΔH = -821.8 kJ (a) Is the reaction exothermic or endothermic? (b) Calculate the amount of heat transferred when 5.6 g of Na reacts at constant pressure. (c) How many grams of NaCl are produced during an
  76. Chemistry

    Consider the following reaction: 2Na + Cl2  2NaCl ΔH = -821.8 kJ (a) Is the reaction exothermic or endothermic? (b) Calculate the amount of heat transferred when 5.6 g of Na reacts at constant pressure. (c) How many grams of NaCl are produced during an
  77. Math

    A gas expands against a constant external pressure of 1.7 bar until its volume has increased from 5.4 L to 8.9 L. During this process it absorbs 640.0 J of heat from the surroundings. Calculate the energy change of the gas.
  78. chemistry

    At 25∘C the reaction from Part A has a composition as shown in the table below. Substance Pressure (atm) C2H2(g) 4.65 H2(g) 3.85 C2H6(g) 5.25×10−2 What is the free energy change, ΔG, in kilojoules for the reaction under these conditions?
  79. CHEMISTRY

    I need help with these problems ASAP: I need help setting these problems up: pleas!! (1)Calculate the volume of 1.87 M NaI that would be needed to precipitate all of the Hg+2 ion from 199 mL of a 1.96 M Hg(NO3)2. The equation for the reaction is 2NaI (aq)
  80. Calorimetry Chemistry

    Please help with these questions. Thanks Consider the reaction C12H22O11(s)+ 12O2(g)-->12CO2(g)+11H2O(l)
  81. CHEMISTRY

    the equilibrium composition of a reaction is 1.522mol CO, 1.566mol H2, 0.478mol CH4 and 0.478mol H2O and the volume of the reaction vessel is 10Litres. -What is the equation for the reaction? -Calculate the equilibrium constant for both the forward and
  82. CHEMISTRY

    A quantity of N2 occupies a volume of 1.5 L at 300 K and 1.2 atm . The gas expands to a volume of 3.2 L as the result of a change in both temperature and pressure.
  83. Physics

    The figure shows a pV diagram of a gas for a complete cycle. During part bc of the cycle, 1190 J of heat flows into a system, and at the same time the system expands against a constant external pressure of 7.00 × 104 Pa as its volume increases from 0.0200
  84. chemistry

    calculate the internal energy change for each of the following. a. one hundred(100.)joules of work are required to compress a gas. at the same time the gas releases 23 J of heat. b. a piston is compressed from a volume of 8.30 L to 2.80 L against a
  85. chemistry

    For a certain chemical reaction, the rate constant at 250.0 °C is 0.00383 s-1 and the activation energy is 22.40 kilojoules. Calculate the value of the rate constant at 335.0 °C. a. 0.00513 s-1 b. 0.00946 s-1 c. 0.00787 s-1 d. 0.0224 s-1 e. 0.000640 s-1
  86. chemistry

    Hi, I am trying to find the pH of a buffer I created and then added NaOH to. This is my data: total volume of solution 34.2 mL [NaOH] before reaction 6.0 [HOAc] before reaction .8 M [OAc-] before reaction .4 M [HOAc] after reaction 0 M [OAc-] after
  87. Grade 12 chemistry

    This is the second reaction: HCl(aq)+NaOH(aq)-->NaCl(aq)+H2O(l) (Heat of neutralization) This reaction involves mixing two solutions: 1.00 mol/L NaOH and 1.00 mol/L HCl. Trial 1: 48.0 mL of the NaOH solution is mixed with 47.5 mL of the HCl. The
  88. civil enginerring

    air having a pressure of 40 psig and a volume of 8 cu ft expands isotermally to a pressure of 10 psig find the external work performed during the expasion
  89. chemistry

    1.)Calculate the number of moles in 3.50 x 10^21 atoms of silver. Show all work. 2.) Calculate the number of atoms in 2.58 mol antimony. Show all work 3.) Determine the mass of 1.45 mol FePO4. Show all work. 4.) Calculate the number of mol in 6.75 g of
  90. chem

    A balloon filled with 22.3 mol helium has a volume of 500. L at 0.0°C and 1.00 atm pressure. The temperature of the balloon is increased to 38.0°C as it expands to a volume of 570. L, the pressure remaining constant. Calculate q, w, and E for the helium
  91. chem

    A balloon filled with 22.3 mol helium has a volume of 500. L at 0.0°C and 1.00 atm pressure. The temperature of the balloon is increased to 38.0°C as it expands to a volume of 570. L, the pressure remaining constant. Calculate q, w, and E for the helium
  92. Chemistry

    I had to perform an experiment for rate of reaction. The point of the experiment was to show how changes in reactant concentration, temperature, and catalyst presence can affect the rate of a reaction. The reaction that we studied was H2O2 + 2I^- + 2H^+ ->
  93. Chemistry2

    WO3 (s) + 3 H2 (g) -> W (s) + 3 H20 (g) Tungsten is obtained commercially by the reduction of WO3 with hydrogen according to the equation above. The following data related to this reaction are available. DeltaH(kilojoules/mole) for WO3 is -839.5. DeltaH
  94. EXAM TMRW

    Calculate the energy in kJ/mol of light with a wavelength of 360 nm. 9.17 * 10^-43 J/mol Oxygen gas at 34.5 °C expands from 34.5 L to 45.7 L against a constant pressure of 750 mmHg. What is the work done in joules by the system? 1.13*10^3 J
  95. Chemistry

    The reaction between 0.045 g of calcium with an excess of water was carried out in an ice calorimeter as used in this lab. The volume of water in the calorimeter decreased by 0.18 mL during the reaction a) Write the equation for the reaction which occurs.
  96. Chemistry

    **When 0.187 g of benzene,C6H6, is burned in a bomb calorimeter, the surrounding water bath rises in temperature by 7.48 C. ** Assuming that the bath contains 250.0 g of water and that the calorimeter itself absorbs a negligible amount of heat, calculate
  97. Chemistry

    How much heat (in kilojoules) is released on reaction of 5.30 g of Al?
  98. ap chemistry :(

    consider the reaction C6H14 + 9.5O2 yields 6CO2 + 7H2O at constant pressure. which response is true? 1. work may be done on or by the system as the reaction occurs, depending upon the temperature. 2. work is done on the system as the reaction occurs. 3. no
  99. chemistry

    I had to do this online lab and have a total of 8 questions at the end and I am stuck half way through. Can someone please walk me through the last few question? Here is the Lab and my homework: In this experiment, we will determine the heat of reaction
  100. ap chem

    A calorimeter contains 20.0 of water at 12.5 . When 2.20 of (a substance with a molar mass of 59.0 ) is added, it dissolves via the reaction and the temperature of the solution increases to 27.5 . Calculate the enthalpy change, , for this reaction per mole