Thermochemistry Flashcards
Unit for quantity of energy
Joules
The enthalpy change for a chemical reaction
Delta H reaction
The energy required to melt a solid at its melting point
The heat of fusion
Hess’ law
If you add two or more Thermal chemical equations to give a final equation you can also add the heat of reaction to give the final heat of reaction
Exothermic reactions
He given to surroundings
Enthalpy
Heat
Final enthalpy value (products) is lower then starting so
It’s value of H is negative
Endothermic reactions
Absorbed from surroundings
Enthalpy of products is higher than starting so
The value of H is positive
Exothermic reactions are written on
The right
Endothermic reactions are written on
The left
Heat is written as a product when
Exothermic and reactant when endothermic
The amount of heat released or absorbed during a reaction depends on
The number of moles of species involved
Quantity applies to
A balanced reaction as written
How is thermal energy transferred between two objects that are different temperatures
He always flows from higher to lower temperatures until they reach the same temperature
What is kinetic energy
Energy of motion
What is heat
Motion of
What is potential energy
Stored energy
What is potential energy stored in
Chemical bonds of compounds
Total energy is
Conserved
What is heat
Energy transferred
What is specific heat of a substance
Heat needed to raise the temperature of 1 g of a substance by 1°C
Energy to freeze or condense
Vapor
Melting or boiling means
Being absorbed
Freezing or condensing
Energy is being released
If a reaction is reversed, the H for the reaction must be
Opposite
What phase changes are endothermic
Melting and evaporation
What the changes are exothermic
Freezing and condensation
In EXOTHERMIC
He given to surroundings
In ENDOTHERMIC
Heat absorbed from surroundings
What’s the difference between calories and joules
They are just two different measurements of the amounts of energy
What happens when energy is change from one form to another
All the energy can be accounted for
What factors do you need to know in order to calculate the heat change in a calorimeter
Heat capacity
Mass that absorbs heat
Temperature change
Describe the energy of a chemical bonds of the reactance an exothermic reactions
Greater than the energy stored in the bonds of the products
When doing an energy change by one mole
Just flip the signs
If the value of H is positive the reaction is
Endothermic
If the value of H is negative the reaction is
Exothermic
What factors are needed and that he capacity of an object
MCAT
Which substance has the highest specific heat capacity
Liquid water
How can you determine the enthalpy for a reaction in an aqueous solution
Mix the reactants in a calorimeter and measure the temperature change
During a state change the temperature of a substance
Remains constant
What is Hess’ law of heat summation
It is used to calculate delta H for complicated chemical reactions
