For a reaction: C(s) + O2(g) → CO2(g) What is the relation between enthalpy of reaction (Δ Hr), enthalpy of formation of CO2 (Δ Hf) and enthalpy of combustion of carbon (Δ Hcomb)?

Question

For a reaction: C(s) + O2(g) → CO2(g) What is the relation between enthalpy of reaction (Δ Hr), enthalpy of formation of CO2 (Δ Hf) and enthalpy of combustion of carbon (Δ Hcomb)? (A) Δ Hr > Δ Hf = Δ Hcomb (B) Δ Hr = Δ Hf = Δ Hcomb (C) Δ Hr = Δ Hf + Δ Hcomb (D) Δ Hr = 2 × Δ Hf

Tardigrade Admin · Accepted Answer

Since the reaction shows combustion of one mole of carbon, Δ Hreaction is enthalpy of combustion since 1 mole of CO2 is formed. Δ Hreaction is also the enthalpy of formation of CO2.

Q. For a reaction : $C_{(s)} + O_{2 (g)} \to C O_{2 (g)}$
What is the relation between enthalpy of reaction $(Δ H_{r})$ , enthalpy of formation of $C O_{2} (Δ H_{f})$ and enthalpy of combustion of carbon $(Δ H_{co mb})$ ?

$Δ H_{r} > Δ H_{f} = Δ H_{co mb}$

$Δ H_{r} = Δ H_{f} = Δ H_{co mb}$

$Δ H_{r} = Δ H_{f} + Δ H_{co mb}$

$Δ H_{r} = 2 \times Δ H_{f}$

Since the reaction shows combustion of one mole of carbon, $Δ H_{re a c t i o n}$ is enthalpy of combustion since $1$ mole of $C O_{2}$ is formed. $Δ H_{re a c t i o n}$ is also the enthalpy of formation of $C O_{2}$ .

Q. For a reaction : C(s)​+O2(g)​→CO2(g)​ What is the relation between enthalpy of reaction (ΔHr​), enthalpy of formation of CO2​(ΔHf​) and enthalpy of combustion of carbon (ΔHcomb​)?

ΔHr​>ΔHf​=ΔHcomb​

ΔHr​=ΔHf​=ΔHcomb​

ΔHr​=ΔHf​+ΔHcomb​

ΔHr​=2×ΔHf​