Question

The standard enthalpy of combustion of formaldehyde Δ₀H⁰ = -571 kJ. How much heat will be evolved in the formation of 22 g of CO₂?

Answer 1

\[\begin{array}{cc}
\ce{O}\phantom{.....................}\\
||\phantom{.....................}\\
\ce{H - C -H +O2 ->CO2 +H2O}
\end{array}\]
Δ_CH = -571 kJ

for 44g of CO₂,  ΔH = -571 kJ

∴ 22g of CO₂,   ΔH = `(22xx-571)/44` = -285.5 kJ