Chapter 14 - Energy changes in chemical reactions Flashcards
What are exothermic reactions?
Reactions that release heat.
What are endothermic reactions?
Reactions that absorb heat
What is thermochemistry?
The study of energy changes in chemical reactions.
What is temperature?
The physical quantity we use to measure the degree of hotness or coldness of an object or substance.
What does specific heat capacity of a substance mean?
The amount of heat required to increase the temperature of unit mass of the substance by exactly 1C.
What is calorimetry?
The measurement and calculation of heat changes.
What formula is used to calculate the quantity of heat absorbed/released?
q=mc∆T
What does ∆T mean?
The change in temperature.
What does q mean in the q=mc∆T formula?
Quantity of heat absorbed.
How do we calculate heat released/absorbed per mole?
total heat release or absorbed/number of moles that reacted
What is enthalpy?
A measure of the total energy possessed by a substance or group of substances.
When a reaction is exothermic is ∆H positive or negative?
Negative.
What does c mean in the q=mc∆T formula?
The specific heat capacity.
What is the change in enthalpy for a chemical reaction ∆H mean?
The heat absorbed per mole of specified reactant or product when the reaction occurs at constant pressure.
When a reaction is endothermic is ∆H positive or negative?
Positive.
Is molar heat of combustion positive or negative?
Positive (because it releases heat).
What is the molar enthalpy of solution/heat of solution?
The heat absorbed when one mole of the substance dissolves in a large excess of water.
What is the law of conservation of energy?
Energy can be neither created nor destroyed but it can be changed from one form to another.
What is ∆H sometimes referred to as?
The heat of reaction.
What is dissociation?
Dissolving ionic substances in aqueous solution to form separated ions.
What is the molar heat of combustion?
The heat liberated when 1 mole of the substance undergoes complete combustion with oxygen at a constant pressure of 100.0 kPa, with the final products being carbon dioxide gas and liquid water.
What is an energy profile?
A diagram which shows the variation of the energy of a reacting system as a function of the progress of the reaction.
Is the enthalpy change for a combustion process and enthalpy of combustion positive or negative?
Negative (because heat is absorbed).
Do catalysts have any effect on the enthalpy change for the reaction?
No.
