Kinetics: Reaction Rates

Question 1

What is the definition of the rate of reaction?

Answer 1

• The change of concentration of reactant/product over time
• The measure of the amount of product formed or reactant used over time
• The units of rate of reaction may be given as g/s, cm3 / s or mol/s

Question 2

What factors will increase the rate of reaction?

Answer 2

• Increase in temperature
• Increase in concentration of reactants
• Increase in pressure of gaseous reactants
• Increase in surface area of solid reactants
• Adding a catalyst

Question 3

What is the effect of temperature on the rate of reaction?

Answer 3

• At higher temperatures, the particles are moving faster, so the collision frequency increases
• Increased movement of the molecules means collisions will occur more often and with greater energy
• Increased temperature increases rate of reaction
• Increases collision frequency
• Increases proportion of successful collisions

Question 4

What is the effect of concentration of reactants on the rate of reaction?

Answer 4

• When the concentration of a sample is increased, more molecules of substance occur in the same volume meaning they are packed closer together
• This increases collision frequency
• Increased concentration increases rate of reaction
• Increases collision frequency
• Speed of particles are the same so the proportion of successful collisions remains the same

Question 5

What is the effect of pressure of gaseous reactants on the rate of reaction?

Answer 5

• When pressure is increased, the gas particles occur in a smaller volume - packed closer together
• This increases collision frequency
• Increased pressure increases rate of reaction
• Increases collision frequency
• Speed of particles are the same so the proportion of successful collisions remains the same

Question 6

What is the effect of surface area of solid reactant on the rate of reaction?

Answer 6

• Increasing the surface area of a solid reactant means a greater surface exposed for collisions
• This means the collision frequency increases, as such there are more successful collisions
• Therefore a faster rate of reaction

Question 7

What is the effect of adding a catalyst on the rate of reaction?

Answer 7

• A catalyst is a substance that increases the rate of a chemical reaction without being changed in chemical composition or amount
• Catalysts work by providing an alternative reaction route of lower activation energy
• Increases rate of reaction
• More particles have sufficient energy so proportion of successful collisions increase
• Collision frequency remains the same