Summary
Summary Unit 3.1.4 - Energetics NOTES
A-level AQA Chemistry Energetics notes New spec Applicable to most exam boards
[Show more]
Connected book
Book Title:
Author(s):
- Edition:
- ISBN:
- Edition:
Seller
Follow
Content preview
Topic 4: EnergeticsEnthalpy change
In a reaction, bonds are broken and then made. For bonds to be broken, energy is taken in
from the surroundings and when bonds are formed, energy is given out. The overall energy
change of the reaction depends on how much energy is transferred in these processes.
When energy is taken in from the surroundings, the enthalpy change is positive. When
energy is released, the enthalpy change is negative.
Overall enthalpy change (∆H) can be calculated:
∆H = (+) energy to break bonds + energy to make bonds (-)
Measuring Enthalpy Change:
Enthalpy is measured under standard conditions of 100 kPa pressure and a temperature of
298 K.
Enthalpy of Formation (∆fH o ):
The enthalpy change when one mole of a substance is produced from its elements under
standard conditions.
Enthalpy of Combustion (∆cH o ):
The enthalpy change when one mole of a substance is burned completely in oxygen under
standard conditions.
Mean Bond Enthalpies:
Different covalent bonds require different amounts of energy to be broken. Values can be
found experimentally using calorimetry methods. The bond enthalpy values calculated in
this way often differ from the data book values as they are not exact and vary in each
situation. This means the data book values are averaged values.
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller anjubellam. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for £2.99. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
52928 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy revision notes and other study material for 14 years now