Question

Suppose the sample had 1-mol% impurity with a heat of combustion 10% larger than that of the compound being studied, for example, napththalene or sucrose. Assuming that the measured heat of combustion of the mixture is a mole-fraction-weighted average of the components, what would be the effect of this impurity on the determined heat of formation of the particular compound

Answer 1

Standard enthalpy of combustion is the change in enthalpy when the compound (napththalene or sucrose) burns in oxygen (O2). The standard enthalpy of formation is the enthalpy change associated with the formation of compound (napththalene or sucrose)  from its constituent elements in their standard states

the sample had impurity, a heat of combustion larger rather than pure compound but in the formation of enthalpy would not be the effect because of  from its atomic constituent as they normally occur in nature