ΔH°
Definition
ΔH°, or standard enthalpy change, is the amount of heat absorbed or released in a reaction at constant pressure and standard conditions (1 atm pressure and 298.15 K).
Analogy
Think of ΔH° like the fuel gauge on your car. Just as the fuel gauge tells you how much gas you've used or gained after a trip, ΔH° tells you how much energy has been absorbed or released during a chemical reaction.
Related terms
Enthalpy (H): The total heat content of a system at constant pressure.
Exothermic Reaction: A chemical reaction that releases heat to its surroundings (ΔH is negative).
Endothermic Reaction: A chemical reaction that absorbs heat from its surroundings (ΔH is positive).
"ΔH°" appears in:
Study guides (1)
Practice Questions (5)
Consider the equation 2 SO₃ (g) ⇌ O₂ (g) + 2SO₂ (g). The ΔH° is -198 kJ/mol. Which of the following would cause the reverse reaction to speed up?
Consider the equation PCL₃ (g) + Cl₂ (g) ⇌ PCl₅ (g). The ΔH° is -92.5 kJ/mol. Which of the following would cause an increase in PCl₅?
Consider the equation N₂ (g)+ 3H₂ (g) ⇌ 2NH₃ (g). The ΔH° is -92.6 kJ/mol. Which of the following statements about concentration after the adjusted equilibrium is NOT true?
If the chemical reaction has a positive ΔH°, what change in temperature produces extra reactants?
Which of the following best helps to explain why the value of ΔH° for the dissolving of CaF2 in water is positive?
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