Define the term enthalpy of reaction

A chemical reaction occurs when bonds are broken and formed between atoms. Energy is taken in in order to break bonds; when a bond is formed the molecule becomes more stable, so energy is given out. The enthalpy of reaction is the net change in energy during a reaction, and is denoted by delta H(dH). When the energy released by bond formation is greater than the energy required to break the bonds, heat is given out, dH is negative, and the reaction is said to be exothermic. If more energy is required to break bonds than is released by bond formation, dH is positive and the reaction is said to be endothermic.The enthalpy of reaction can be calculated by adding up the bond energies of the reactants and subtracting the bond energies of the products.

Answered by Harry K. Chemistry tutor

1627 Views

See similar Chemistry A Level tutors

Related Chemistry A Level answers

All answers ▸

Give the molecular formula of benzene. Give the Kekule structure of benzene and then explain why this structure is not correct. Give the accepted structure for benzene (5 marks).


25cm^3 of 0.1M NaOH is reacted with 0.01M HCl until the equivalence point is reached. What volume of HCl was required to be added?


Explain why the second ionisation energy of boron is higher than the first ionisation energy of boron.


Q1. Two beakers, A and B, each contain 100.0 cm^3 of 0.0125 mol/dm^3 nitric acid. Calculate the pH of the solution formed after 50.0 cm^3 of distilled water are added to beaker A. Give your answer to 2 decimal places.


We're here to help

contact us iconContact usWhatsapp logoMessage us on Whatsapptelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo

© MyTutorWeb Ltd 2013–2024

Terms & Conditions|Privacy Policy
Cookie Preferences