Beyond Science returns with this A Level blog on Energetics. In our modern world, where we rely heavily on energy resources – it is essential that we are able to accurately measure and calculate the energy changes that take place during chemical reactions. This is what you will discover how to do while studying Energetics. Here you’ll find the answers to FAQs about some of the key concepts and terminology you’ll encounter in the A Level Chemistry Energetics topic.
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What is an exothermic reaction?
What is an endothermic reaction?
What is enthalpy change (βH)?
What is standard enthalpy change (βHΒ°)?
What is standard enthalpy of combustion (βCHΞΈ)?
What is standard enthalpy of formation (βfHΞΈ)?
What is standard enthalpy of reaction (βrHΞΈ)?
What is the equation used to calculate the heat change of a reaction (q)?
What is an exothermic reaction?
An exothermic reaction is a reaction in which more energy is released to the surroundings by the formation of chemical bonds than is taken in from the surroundings to break chemical bonds. In an exothermic reaction, ΞH is negative.
What is an endothermic reaction?
An endothermic reaction is a reaction in which more energy is taken in from the surroundings to break chemical bonds than is released to the surroundings by the formation of chemical bonds. In an endothermic reaction, ΞH is positive.
What is enthalpy change (βH)?
Enthalpy change is the heat energy change measured under conditions of constant pressure.
What is standard enthalpy change (βHΒ°)?
Standard enthalpy change is the heat energy change measured under standard conditions of 100kPa pressure and a stated temperature.
What is standard enthalpy of combustion (βCHO)?
Standard enthalpy of combustion is the enthalpy change when 1 mole of a substance reacts completely with oxygen under standard conditions.
What is standard enthalpy of formation (βfHO)?
Standard enthalpy of formation is the enthalpy change when 1 mole of a compound is formed from its elements in their standard states under standard conditions.
What is standard enthalpy of reaction (βrHΞΈ)?
Standard enthalpy of reaction is the enthalpy change when a chemical reaction takes place in the molar quantities shown in the chemical equation under standard conditions.
What is the equation used to calculate the heat change of a reaction (q)?
q = mcΞT
q = heat change of the reaction
m = mass of the substance that has a temperature change
c = specific heat capacity
ΞT = change in temperature
What is calorimetry?
Calorimetry is a practical method used to measure the heat energy change of a chemical reaction.
What is mean bond enthalpy?
Mean bond enthalpy is the average energy required to break a particular covalent bond, averaged over a range of compounds containing that bond.
What is Hess’s law?
The overall enthalpy change of a reaction is always the same no matter what route the chemical reaction takes.
What is standard state?
Standard state is the physical state of a substance under standard conditions (100kPa and a stated temperature).
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