The required specific heat capacity of the substance is 126 J/kg-K.

Given,

mass (m) = 500 g = $\rm \frac{500}{1000} kg$ = 0.500 kg

initial temperature (T$\rm _{1}$) = 100$\rm ^{o}$C

final temperature (T$\rm _{2}$) = 226$\rm ^{o}$C

quantity of heat (Q) = 7938 J

To find: s = ?, where s is the specific heat capacity of the substance.

By using the formula for the quantity of heat, we get,

$\rm Q = ms \cdot \triangle T$

$\rm or, s = \frac{Q}{m \triangle T}$

$\rm or, s = \frac{Q}{m ( T_{2} - T_{1} )}$

$\rm or, s = \frac{7938}{0.500 \cdot (226 - 100)}$

$\rm \therefore s = 126 J/kg-K$