Physical Chemistry Flashcards
What does the law of conservation of energy state?
Energy cannot be created or destroyed, only moved from one place to another.
What is an endothermic reaction?
A reaction in which the more energy is needed to make bonds than is released breaking bonds, resulting in heat being taken in from the surroundings.
What is an exothermic reaction?
A reaction in which the more energy is released breaking bonds than is needed to make bonds, resulting in heat being taken in from the surroundings.
What is activation energy?
The minimum energy required to to start a reaction by breaking bonds in the reactants.
What are the values of the standard conditions?
100 kPa, 298k, 1 mol/dm3
What is the enthalpy change of a reaction?
The energy change associated with a given reaction.
What is the enthalpy change of formation?
The energy change that takes place when one mole of a compound is formed from its constituent elements in their standard states under standard conditions.
What is the enthalpy change of combustion?
The energy change that takes place when one mole of a substance is completely combusted in oxygen.
What is the enthalpy change of neutralisation?
The energy change associated with the formation of one mole of water from a neutralisation reaction.
What does Hess’ law state?
The enthalpy change of a reaction is independent of the route it takes.
What factors affect the rate of a chemical reaction?
temperature, pressure and concentration, surface area and whether or not a catalyst is present.
How do you calculate a rate of reaction from a concentration-time graph?
Draw a tangent and find the gradient of it.
What is a catalyst?
A substance that increases the rate of a reaction without being used up in the process.
What is a homogeneous catalyst?
A catalyst that is in the same phase as the reactants.
What is a heterogeneous catalyst?
A catalyst that is in a different phase to the reactants.
