Topic 1: Equilibrium Flashcards
Explain what ‘surroundings’ and ‘system’ refers to by constructing a diagram
A system is the chemical reaction being studied and the surroundings are everything else.
Define thermochemical equations
Chemical equations which show the heat released or absorbed during the reaction by stating the change in enthalpy (∆H)
Define activation energy
Energy required to break the bonds of the reactants so that the reaction proceeds
Define a catalyst
A substance which increases reaction rate by lowering the activation energy but does not partake in the reaction, so it remains unchanged.
Distinguish between an exothermic and endothermic reaction
An exothermic reaction release energy into the surroundings due to its products having less enthalpy than its reactants as indicated by a negative ∆H value.
Contrarily, endothermic reactions absorb energy from their surroundings to form bonds meaning the products have a higher enthalpy than their reactants as indicated by a positive ∆H value.
Distinguish between homogenous and heterogenous systems
Homogenous systems have all substances in the same state (solid/liquid/gas) whereas heterogenous systems are composed of substances in varying states - like gases and solids.
Identify the relationship between ∆H (Change in Enthalpy) and the reaction type
Exothermic reactions have a negative ∆H value whereas endothermic reactions have a positive ∆H value
Construct energy profiles for an exothermic and endothermic. Hence compare the two reaction types.
Exothermic reactions involve reactants with a higher energy that release energy as the reaction takes place, forming products with a lower energy.
Endothermic reactions have the opposite mechanism, where they involve reactants with a lower energy that absorb energy to produce products with a higher energy.
Use energy profiles of exothermic and endothermic reactions to explain the reversibility of reactions with reference to activation energy
The forward reaction can be reversed where the products can be reacted to form products.
If the forward reaction is exothermic with a low activation energy than the reverse reaction would be endothermic with a higher activation energy.
Use an energy profile to demonstrate how a catalyst affects rate of reaction
Catalysts lower the activation energy meaning more particles have sufficient energy to undergo a reaction which increases reaction rate
Explain the reversibility of chemical equations by considering their activation energies
When particles collide, the energy associated with collisions can break bonds in reacting particles, allowing them to rearrange to form new products where the energy required to break or weaken the bonds of the reactants is the activation energy.
In the reverse reaction, once the products form, if the product particles collide with enough energy to break their bonds (the activation energy of the reverse reaction) it is possible to re-form the reactant
Describe how the enthalpy changes if the reaction is reversed
If the reaction is reversed, the sign on the enthalpy (∆H) changes.
Explain collision theory and how it relates to reactions
Collision theory is used to predict the rate of reactions.
It states that for a reaction to occur particles **must collide with sufficient energy and the correct orientation. **
Resultantly, increasing the number of collisions per minute with sufficient energy increases reaction rate.
Define chemical equilibrium
Chemical equilibrium is the state in which both reactants and products are produced at equal rates.
Explain what is meant by a ‘dynamic’ chemical equilibrium
The reaction does not stop occurring.
Instead, the rate of the forward and reverse reaction is at the same rate such that the concentrations remain the same.
