Given the thermochemical equations x2 +32 2xYAH = -340kJ -> -> ΔΗ *2+2Z2 - 2xZ2,AH2 = -180kJ 2Y2 + Z2 -2Y, Z, AH, H = -250kJ 2 Calculate the change in enthalpy for the reaction. 3 4xY₂ +7Z +7Z2 -> 6Y2Z+4x2 AH =

Benzoic acid, C6H5COOH, is a common standard used in bomb calorimeters, which maintain a constant volume. If 1.20 g of benzoic acid gives off 31, 723 J of energy when burned in the presence of excess oxygen and in a water bath having a temperature of 24.6 C, calculate q, w, H, and U for the reaction.

The octane number of gasoline is based on a comparison of the gasolines behavior with that of 2,2,4-trimethylpentane, C8H18(), which is arbitrarily assigned an octane number of 100. The standard enthalpy of combustion of this compound is 5456.6 kJ/mol. (a) Write the thermochemical equation for the combustion of 2,2,4-trimethylpentane. (b) Use the standard enthalpies of formation in Appendix G to calculate the standard enthalpy of formation of 2,2,4-trimethylpentane.

Acetylene (C2H2) and butane (C4H10) are gaseous fuels with enthalpies of combustion of 49.9 kJ/g and 49.5 kJ/g. respectively. Compare the energy available from the combustion of a given volume of acetylene to the combustion energy from the same volume of butane at the same temperature and pressure.

A student is asked to calculate the amount of heat involved in changing 10.0 g of liquid bromine at room temperature (22.5C) to vapor at 59.0C.To do this, one must use Tables 8.1 and 8.2 for information on the specific heat, boiling point, and heat of vaporization of bromine. In addition, the following step-wise process must be followed. (a) Calculate H for: Br2(l,22.5C)Br2(l,59.0C) (b) Calculate H for: Br2(l,59.0C)Br2(g,59.0C) (c) Using Hess's law, calculate H for: Br2(l,22.5C)Br2(g,59.0C)

What is the heat gained/released at constant pressure equal1o (qp = ?)? What is the heat gained/released at constant volume equal to (qv = ?)? Explain why H is obtained directly from a coffee-cup calorimeter, whereas E is obtained directly from a bomb calorimeter.

Combustion reactions involve reacting a substance with oxygen. When compounds containing carbon and hydrogen are combusted, carbon dioxide and water are the products. Using the enthalpies of combustion for C4H4 ( 2341 kJ/mol), C4H8 (2755 kJ/mol), and H2 (286 kJ/mol), calculate H for the reaction C4H4(g)+2H2(g)C4H8(g)

A 220-ft3 sample of gas at standard temperature and pressure is compressed into a cylinder, where it exerts pressure of 2000 psi. Calculate the work (in J) performed when this gas expands isothermally against an opposing pressure of 1.0 atm. (The amount of work that can be done is equivalent to the destructive force of about 1/4 lb of dynamite, giving you an idea of how potentially destructive compressed gas cylinders can be if improperly handled!)

sample of natural gas is analyzed and found to be88.4% methane (CH4) and 11.6% ethane (C2H6) bymass. The standard enthalpy of combustion of methaneto gaseous carbon dioxide (CO2) and liquid water (H2O) is -891 kJ/mol. Write the equation for the combustionof gaseous ethane to carbon dioxide and water.Calculate the standard enthalpy of combustion of ethaneusing standard enthalpies of formation from Table R-11on page 975. Using that result and the standard enthalpyof combustion of methane in Table 15.3, calculate theenergy released by the combustion of 1 kg of natural gas.

Starting with equation 2.27 andthe original definitionof enthalpy, derive the fact that Cp-=Cv-+R