Using the table of average bond energies below, the AH for the reaction is kJ. HH H-CEC-H(g) + 2HI (g) → I-C-C-I (g) HH Bond: C=C C-CH-I C-I C-H D 839 348 299 240 413 (kJ/mol): -217 -160 +63 +160 -63

Explain why H is obtained directly from coffee-cup calorimeters, whereas E is obtained directly from bomb calorimeters.

A 0.470-g sample of magnesium reacts with 200 g dilute HCl in a coffee-cup calorimeter to form MgCl2(aq) and H2(g). The temperature increases by 10.9 C as the magnesium reacts. Assume that the mixture has the same specific heat as water and a mass of 200 g. (a) Calculate the enthalpy change for the reaction. Is the process exothermic or endothermic? (b) Write the chemical equation and evaluate H.

1. For the reaction 2 Hg(l) + O2(g) → 2 HgO(s), ∆rH° = 181.6 kJ/mol-rxn. What is the enthalpy change to decompose 1.00 mol of HgO(s) to O2(g) and Hg(l)? 3633 kJ −90.8 kJ 90.8 kJ 363.3 kJ

The equation for the fermentation of glucose to alcohol and carbon dioxide is: C6H12O6(aq) 2C2H5OH(aq) + 2CO2(g) The enthalpy change for the reaction is 67 kJ. Is this reaction exothermic or endothermic? Is energy, in the form of heat, absorbed or evolved as the reaction occurs?

The heat of neutralization, Hneut, can be defined as the amount of heat released (or absorbed), q, per mole of acid (or base) neutralized. Hneut for nitric acid is -52 kJ/mol HNO3. At 27.3C, 50.00 mL of 0.743M HNO3 is neutralized by 1.00 M Sr(OH)2 in a coffee-cup calorimeter. (a) How many mL of Sr(OH)2 were used in the neutralization? (b) What is the final temperature of the resulting solution? (Use the assumptions in Question 11.)

Write reactions for which the enthalpy change will be a. Hf for solid aluminum oxide. b. the standard enthalpy of combustion of liquid ethanol, C2H5OH(l). c. the standard enthalpy of neutralization of sodium hydroxide solution by hydrochloric acid. d. Hf for gaseous vinyl chloride, C2H3Cl(g). e. the enthalpy of combustion of liquid benzene, C6H6(l). f. the enthalpy of solution of solid ammonium bromide.

At 298 K, the standard enthalpies of formation for C2H2(g) and C6H6(l) are 227 kJ/mol and 49 kJ/mol, respectively. a. Calculate H for C6H6(l)3C2H2(g) b. Both acetylene (C2H2) and benzene (C6H6) can be used as fuels. Which compound would liberate more energy per gram when combusted in air?

Although the gas used in an oxyacetylene torch (Figure 5.7) is essentially pure acetylene, the heat produced by combustion of one mole of acetylene in such a torch is likely not equal to the enthalpy of combustion of acetylene listed in Table 5.2. Considering the conditions for which the tabulated data are reported, suggest an explanation.

When 2.50 g of methane burns in oxygen, 125 kJ of heat is produced. What is the enthalpy of combustion per mole of methane under these conditions?