What is enthalpy?
Enthalpy (given the symbol H) is a measure of how much heat energy can be released by a chemical. ΔH is defined as the amount of heat energy released or taken in when two chemicals react. If ΔH is negative it means that the reaction is exothermic and will give out heat as it progresses and will feel hot.
If ΔH is positive then the reaction is endothermic and will therefore absorb heat as it progresses, and will feel cold.
CM
Related Chemistry A Level answers
All answers ▸Calculate the pH of a 0.025 mol dm-3 solution of methanoic acid. For HCOOH, Ka = 1.58 x 10-4 mol dm-3
At 25 °C, the initial rate of reaction is 3.1 × 10−3 mol dm−3 s−1 when the initial concentration of C is 0.48 mol dm−3 and the initial concentration of D is 0.23 mol dm−3 . Calculate a value for the rate constant at this T when rate = k [C][D].
Explain the geometry and bond angles in a NH3 molecule
How does HBr add across a double bond? Predict the regiochemistry when HBr is reacted with 2-methylpropene