Step 1: Understanding the Concept
\(\Delta G^{\circ}=\Delta H^{\circ}-T\Delta S^{\circ}\) with \(T=298\ \text{K}\) (standard).
Step 2: Unit conversion
\(\Delta S^{\circ}=-21\ \mathrm{J\,K^{-1}}=-0.021\ \mathrm{kJ\,K^{-1}}\).
Step 3: Substitute
\(\Delta G^{\circ}=219-298\times(-0.021)=219+6.258\).
Step 4: Result
\(\Delta G^{\circ}\approx225.26\ \mathrm{kJ}\).
Final Answer:
The standard Gibbs energy change is about 225.26 kJ.
\[ \boxed{\text{(C) }225.26\text{ kJ}} \]