Hess's law is analogous to:
Correct answer: B. 1st law of thermodynamics
- A. Law of heat summation
- B. 1st law of thermodynamics
- C. Law of increasing entropy
- D. Law of heat exchange
Explanation
Hess's Law is a direct consequence of the First Law of Thermodynamics and the fact that enthalpy is a state function. It states that the total enthalpy change for a reaction is independent of the path taken, which reflects the principle of conservation of energy.
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About Hess's Law
Hess's law states that the enthalpy change of a reaction is independent of the route because enthalpy is a state function. Calculations involve reversing and adding thermochemical equations, using standard enthalpies of formation or combustion, and finding an unknown reaction enthalpy without confusing enthalpy change with reaction rate.
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Combustion of graphite to form CO2 can be done by two ways. Reactions are given as follows: 1.C + O2 -> CO2 ∆H = -393.7 kJ mol-12.C + ½O2 -> CO ∆H = ?3.CO + ½O2 -> CO2 ∆H = -283 kJ mol-1What will be the enthalpy of the formation of CO?
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Given that C + O2 gives CO2 has an enthalpy change of minus 393 kJ per mole, and CO + half O2 gives CO2 has an enthalpy change of minus 283 kJ per mole, the enthalpy of formation of carbon monoxide is
Hess's law states that the enthalpy change of a reaction
Standard enthalpy of combustion of graphite at 25 °C is -393.51 kJ mol-1 and that of diamond is -395.41 kJ mol-1. The enthalpy change for graphite is: