What is a standard enthalpy of formation?
AThe heat change when one mole of a compound burns fully
BThe heat change forming one mole from its stable elements
CThe heat change forming any amount from any starting mixture
DThe heat change when one mole of a compound is decomposed
Answer & Solution
Correct answer: B. The heat change forming one mole from its stable elements
1. The reaction must form exactly 1 mole of the pure substance.
2. The starting materials must be the free elements in their most stable states.
3. Conditions must be the standard state conditions.
4. Fractional coefficients on the element side are allowed, since the product must stay at 1 mole.
_Source: OpenStax Chemistry (CC BY 4.0), Ch 5 "Thermochemistry", section 5.3 Enthalpy_
Related questions
The energy needed to raise the temperature of water depends on atmospheric pressure and onThe specific heat of a substance is usually treated as constant across a chapter's temperaA flask of water heated from 21 degrees Celsius to 85 degrees Celsius has absorbed heat, sHeating 800 grams of water by one degree Celsius requires how many times the energy neededCompared with chemical reactions, the energy changes in nuclear reactions are larger by a Increasing the thermal energy of a sample raises its temperature, provided that:In a bimetallic strip thermometer, brass and steel are paired because on heating:Most metals have specific heats that are: