Reaction Rates and Equilibrium

Flashcards about reaction rates and equilibrium.

What is the rate of a chemical reaction?

The speed at which reactants are chemically converted into products.

According to collision theory, what conditions must be met for a reaction to occur?

Reacting particles must collide, collide with the correct orientation, and collide with sufficient energy.

What does an energy profile diagram show?

Shows the changes in potential energy of the substances involved in a chemical reaction.

What information does an energy profile diagram display?

Activation energy, change in enthalpy, energy of reactants, and energy of products.

How does the nature of the reactants affect reaction rate?

A chemical reaction that has less bond breaking and bond forming will naturally be faster.

How does concentration affect reaction rate?

Increasing the concentrations of reactants can increase the rate of a chemical reaction.

Why does increasing concentration increase the reaction rate?

It leads to an increased frequency of collisions and a greater proportion of successful collisions.

How does pressure/volume affect reaction rate?

Increasing the pressure (or decreasing the volume) can increase the rate of a chemical reaction.

Why does increasing pressure increase the reaction rate?

It leads to an increased frequency of collisions and a greater proportion of successful collisions.

What does 'state of subdivision of the reactants' mean?

The overall surface area of the reactants.

How does the state of subdivision affect reaction rate?

Increasing the surface area increases the number of reactant particles exposed and available for collisions.

How does agitation affect reaction rate?

By creating movement in a fluid, reacting particles are more exposed for collisions, and are given more kinetic energy.

How does temperature affect reaction rate?

An increase in temperature can increase the rate of a chemical reaction.

Why does increasing temperature increase the reaction rate?

Collision frequency increases, and more particles have energy greater than the activation energy.

How does a catalyst affect reaction rate?

Catalysts increase reaction rate by providing an alternate reaction pathway that has a lower activation energy.

What is a catalyst?

Something that can alter the rate of a chemical reaction.

What is a chemical system?

The environment in which a chemical reaction occurs.

What is the difference between an open and closed chemical system?

An open system exchanges matter and energy with its surroundings, while a closed system only exchanges energy.

What is an advantage of an open chemical system?

Simple to use, easy to add reactants or remove products, low cost of operation.

What is a disadvantage of using an open chemical system?

Easy to lose sample, reaction mixture can be contaminated, difficult to control and monitor reaction conditions.

What is an advantage of a closed chemical system?

No sample loss or contamination, easier to control conditions, greater yield of products.

What is a disadvantage of using a closed chemical system?

More complex, system has to be opened to add or remove materials, higher cost of operation.

What is equilibrium?

When the rate of the forward reaction is equivalent to the rate of the reverse reaction.

What is meant by 'dynamic'?

The forward and reverse reactions are still occurring.

Describe the reaction rate of a system at equilibrium.

The rate of the forward reaction is equal to the rate of the reverse reaction.

Describe the concentration of substances in a system at equilibrium.

The concentrations of each substance involved in the reaction will be unchanging.

Describe a system at 'phase equilibrium'.

The rate of evaporation is equal to the rate of condensation.

Describe a system at 'solution equilibrium'.

The rate at which a solid dissolves in a solution is equal to the rate at which it re-crystallises.

What does the equilibrium constant compare?

Compares the concentration of reactants to products.

Do the reactants or the products appear in the numerator of an expression?

Products.

Which states of matter must be omitted from an expression?

Liquid or solid.

What does it mean by 'the forward reaction is favoured'?

The rate of the forward reaction increases greater that the rate of the reverse reaction OR the rate of the forward reaction decreases to a lesser extent than the reverse reaction.

What does it mean by 'the reverse reaction is favoured'?

The rate of the reverse reaction increases greater than the rate of the forward reaction OR the rate of the reverse reaction decreases to a lesser extent than the forward reaction.

How does a small value of K relate to equilibrium position?

The reverse reaction is favored or that the equilibrium position is toward the left.

How does a large value of K relate to equilibrium position?

The forward reaction is favored or that the equilibrium position is towards the right.

What is a reaction quotient?

Provides a measurement of the relative amounts of products and reactants present in a reaction mixture at a specific point in time.

How is a reactant quotient different from an equilibrium constant?

K describes a reaction at equilibrium, while Q describes a non-equilibrium situation.

What effect does concentration have on the equilibrium constant?

Concentration has no effect on the equilibrium constant.

What effect does temperature have on the equilibrium constant?

Temperature will change the equilibrium constant.

How does the energy of products compare to the energy of reactants in an exothermic reaction?

The energy of products is lower than the energy of reactants.

What occurs in the environment when an exothermic reaction occurs?

Energy is released into the surroundings.

How does the energy of products compare to the energy of reactants in an endothermic reaction?

The energy of the products is higher than the energy of the reactants.

What occurs in the environment when an endothermic reaction occurs?

Energy is absorbed from the surroundings.

What is the relationship between pressure and volume?

Volume is inversely proportional to pressure.

How does a catalyst affect equilibrium yield?

Equilibrium yield is not affected.