IGCSE CIE Chemistry - Rates of reaction

Reaction rates

And Limiting factors

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Exo-Endo thermic

Activation Energy

and Collision Theory

Activation Energy - minimum amount of energy colliding particles must have to react.

Collision theory -

particles must collide, with surface energy, at the proper orientation.

Higher number of collision, higher the reaction rate.

Multiple Choice

Exothermic reactions release heat to the surroundings.

• true

• false

Multiple Choice

Activation energy is required to start a chemical reaction. What is activation energy?

• The energy needed for a reaction to occur

• The minimum amount of energy needed for a reaction to potentially occur

• The energy added by a catalyst

• The energy possessed by the products

Multiple Choice

What letter represents the activation energy?

• A

• B

• C

• D

Multiple Choice

What is collision theory?

• Molecules must collide in the correct orientation with enough energy to bond.

• Molecules need enough energy to collide and react.

• Atoms constantly collide and react.

• The minimum energy needed for atoms to react

Multiple Choice

If the reactant particles collide with less than the activation energy, the particles will be rebound, and no reaction will occur.

• True

• False

Multiple Choice

What is the rate of reaction?

• How much energy is needed for a reaction to occur.

• The energy required to break a bond.

• The time it takes for a reaction to occur.

• Collision Theory

Multiple Choice

What is the purpose of a catalyst?

• Helps to slow down a reaction

• Raises the activation energy

• Lowers the activation energy

• Is consumed by the reaction

Multiple Choice

What factors effect rate of reaction?

• Temperature, Concentration, Pressure and Energy

• Surface Area, Concentration, Energy and Pressure

• Temperature, Pressure, Concentration and Surface area

• Pressure, Surface area, Density and Energy

Multiple Choice

Increasing the temperature of your solution will.......

• Not affect the rate of reaction.

• Speed up the rate of reaction

• Slow down the rate of reaction

Multiple Choice

Increase in temperature of the reactants can do one of the following

• Slow collision frequency

• Allow less effective collision between the particles

• Cause particles to lose speed

• Increase collision between the particles thus increasing the rate.

Multiple Choice

Grinding a seltzer tablet into powder increases the rate of reaction due to increased

• concentration

• surface area

• temperature

• reactants

Multiple Choice

A ______________ is a substance that increases the rate of a reaction without being used up during the reaction. 

• catalyst

• product

• reactant

• solute

Multiple Choice

Why does a higher concentration increase the rate of reaction?

• it increases the amount of reactants

• it lowers the activation energy

• it increases the energy of particle collisions

• it increases the frequency of particle collisions because there are more collision sites

Rates of Reaction

• The rate of reaction is simply the speed at which a reaction takes place.

• The units of the rate of reaction: g s^-1 or cm³ / dm³ s^-1, which can then be converted into mol dm³ s^-1.

The word equation for the reaction of calcium carbonate with hydrochloric acid

The table shows results obtaining using this apparatus

The graph of the results is plotted

it is easier to see the pattern that they make.

Reaction Rates

How fast a reaction goes

Multiple Choice

Why does a higher temperature increase the rate of a reaction?

• it increases both the frequency and energy of particle collisions

• it only increases the frequency of particle collisions

• it only increases the energy of particle collisions

• it reduces the activation energy of the reaction

Multiple Choice

Grinding a seltzer tablet into powder increases the rate of reaction due to increased

• concentration

• surface area

• temperature

• reactants

Multiple Choice

The following graph shows two different reaction pathways for the same overall reaction at the same temperature. Which pathway is slower and why?

• Red, because the activation energy is larger

• Blue, because the activation energy is lower

• both reaction progress at the same rate