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

CRS Question, 6–26

ANSWER

Choice 2 provides the correct sign and value. The moles of each reactant must be multiplied by the heat of formation of each component (noting their physical state), then the sum of the enthalpy for reactants is subtracted from the sum of the enthalpies of the products (noting that oxygen has a zero for enthalpy of formation).

Section 6.4: Standard Enthalpies of Formation