Same chapter3 marksDifficulty: Medium
Calculate the enthalpy change of a reaction whose bond enthalpies give 1,200 kJ absorbed to break bonds and 1,500 kJ released to form them.
Chemical Thermodynamics
3 marksDifficulty: Medium
Define enthalpy of formation and enthalpy of combustion.
Original Khojo Papers practice question — not from a past board paper.
Answer
The enthalpy of formation is the enthalpy change when one mole of a compound is formed from its elements in their standard states. The enthalpy of combustion is the enthalpy change when one mole of a substance is completely burnt in oxygen under standard conditions.
No citable source has been recorded for this record. Treat it as practice material, not as fact.
Explanation
Enthalpies of combustion are always negative, because combustion is exothermic.
Related questions
From the same topic and chapter, at a similar level.
Same chapter3 marksDifficulty: Medium
What is entropy, and how does it change when a solid melts and when a gas is compressed?
Chemical Thermodynamics
Same chapter3 marksDifficulty: Medium
State Hess's law and give one use of it.
Chemical Thermodynamics
Same chapter3 marksDifficulty: Medium
State the relation between Gibbs energy, enthalpy and entropy, and the condition for a spontaneous process.
Chemical Thermodynamics
Same chapter3 marksDifficulty: Medium
Distinguish between an open, a closed and an isolated system, with one example of each.
Chemical Thermodynamics
Same subject3 marksDifficulty: Medium
State Hund's rule and the Aufbau principle.
Structure of Atom