Energy Changes Flashcards
What does ‘Q’ stand for in the energy change equation?
Energy change (in Joules)
What does ‘m’ stand for in the energy change equation?
Mass OF THE SOLUTION (where 1cm3 = 1g)
What does ‘c’ stand for in the energy change equation?
Specific heat capacity (always 4.18)
What does ‘delta T’ stand for in the energy change equation?
Change in temperature (*C)
What is the equation for energy change?
Q = m x c x delta T
What is the symbol for enthalpy change?
Delta H
What is the equation for molar enthalpy change?
Delta H = Q / Moles
What is the equation for moles used in enthalpy calculations?
Moles = Concentration x Volume / 1000
OR
Moles = Mass / Mr
What are the steps for calculating enthalpy change?
- Find the energy change for the reaction
- Find the moles of the fuel
- Find the enthalpy change (delta H)
What is an exothermic reaction?
One that releases energy.
What is an endothermic reaction?
One that takes in energy.
In an energy level diagram, if the products are lower in energy than the reactants, the reaction is…
Exothermic
In an energy level diagram, if the products are higher in energy than the reactants, the reaction is…
Endothermic
If delta H is positive, the reaction is…
Endothermic
If delta H in negative, the reaction is…
Exothermic
Is the breaking of bonds exothermic or endothermic?
Endothermic (it requires energy to happen)
Is the making of bonds exothermic or endothermic?
Exothermic
To calculate energy change per mole using bond energies, you…
Take away the bonds formed in the products from the bonds broken in the reactants.
