? asked in Science & MathematicsChemistry · 9 years ago

# what is the enthalpy of formation of hexane (C6H14) given that the enthalpy of combustion of hexane is?

-4163.2 kJ/mol, the enthalpy of formation of carbon dioxide is -393.5 kJ/mol and the enthalpy of formation of water is -28508?

a) +67.1 kJ/mol

b) +198.4 kJ/mol

c)-198.4 kJ/mol

d) -67.1 kJ/mol

Update:

Its -285.8

Relevance
• 9 years ago

Combustion reaction is:

C₆H₁₄ + (19/2) O₂ → 6 CO₂ + 7 H₂O

The enthalpy of combustion is nothing else than the enthalpy of the combustion reaction:

According to Hess' law, enthalpy of reaction equals the difference of the enthalpies of formation of products and reactants:

∆Hr = (∑ ∆Hf)_products - (∑∆Hf)_reactants = 6∙∆Hf(CO₂) + 7∙∆Hf(H₂O) - ∆Hf(C₆H₁₄) - (19/2)∙∆Hf(O₂)

Since the enthalpy of formation of the elements at their standard state equals zero:

∆Hr = 6∙∆Hf(CO₂) + 7∙∆Hf(H₂O) - ∆Hf(C₆H₁₄)

Hence,

∆Hf(C₆H₁₄) = 6∙∆Hf(CO₂) + 7∙∆Hf(H₂O) - ∆Hr

= 6∙(-393.5 kJ/mol) + 7∙(285.8 kJ/mol) - (-4163.2 kJ/mol)

= -198.4 kJ/mol

Lv 4
3 years ago

Enthalpy Of Combustion

• 3 years ago

Enthalpy Of Formation

• 5 years ago

RE:

what is the enthalpy of formation of hexane (C6H14) given that the enthalpy of combustion of hexane is?

-4163.2 kJ/mol, the enthalpy of formation of carbon dioxide is -393.5 kJ/mol and the enthalpy of formation of water is -28508?

a) +67.1 kJ/mol

b) +198.4 kJ/mol

c)-198.4 kJ/mol

d) -67.1 kJ/mol

Source(s): enthalpy formation hexane c6h14 enthalpy combustion hexane is: https://shortly.im/fYgxv