Figure 1.01a: (a.)The surface of a single grain of table salt.

CRS Question, 6–25

QUESTION

Using information from Appendix Four, determine the standard enthalpy change at 25°C for the combustion of one mole of heptane (C7H16) sometimes used in gasoline fuel mixtures. The balanced equation is shown here:

C7H16 (g) + 11 O2 (g) ® 7 CO2 (g) + 8 H2O (l)

(Note: the standard molar enthalpy change of formation of C7H16 (g) is –264 kJ/mol)

1. –4430 kJ

2. –4800 kJ

3. –5310 kJ

4. This can’t be solved without the heat of formation of oxygen.