Physical Chemistry - Rates of Reaction

Question 1

what is the equation for rate of reaction?

Answer 1

rate of reaction = amount of reactant used or product created/time

Question 2

how would you investigate rates of reaction?

Answer 2

• marble chips react with hydrochloric acid (HCl) to produce carbon dioxide gas and calcium chloride solution
• add marble chips to hydrochloric acid in a beaker with cotton wool on the top (so carbon dioxide can escape but no acid can)
• measure with a balance
• measure the mass of carbon dioxide lost at intervals
• vary the surface area of the marble chips, the concentration of acid or the temperature.

Question 3

how would you investigate the effects of the use of a catalyst on the rate of a reaction?

Answer 3

• hydrogen peroxide naturally decomposes slowly producing water and oxygen gas, manganese (IV) oxide can be used as a catalyst to speed up the rate of reaction
• the rate of reaction can be measured by measuring the volume of oxygen produced at regular intervals using a gas syringe

Question 4

what happens to rate of reaction when surface area increases?

Answer 4

increasing the surface area of a solid increases the rate of a reaction
- more particles exposed
- more frequent collisions per unit time
- increase the rate of a reaction

Question 5

what happens to rate of reaction when concentration increases?

Answer 5

increasing the concentration of a solution increases the rate of a reaction
- more particles in same space
- more frequent collisions per unit time
- increase rate of reaction

Question 6

what happens to rate of reaction when pressure increases?

Answer 6

increasing the pressure of a gas increases the rate of a reaction

Question 7

what happens to rate of reaction when temperature increases?

Answer 7

increasing the temperature increases the rate of a reaction
- particles have more kinetic energy
- more frequent collisions and a higher proportion of those collisions are successful because the collision energy is greater or equal to the activation energy
- increase rate of reaction

Question 8

what happens to rate of reaction when a catalyst is used?

Answer 8

using a catalyst increases the rate of a reaction

Question 9

what is a catalyst?

Answer 9

a catalyst is a substance that increases the rate of a reaction (by providing an alternate pathway with a lower activation energy) but is chemically unchanged at the end of the reaction.

Question 10

what catalysts could be used to investigate which is most effective in decomposing hydrogen peroxide?

Answer 10

• manganese dioxide
• liver
• potato
• potassium iodide
• copper oxide
• sodium chloride
  only some of these are effective catalysts when used with hydrogen peroxide. if they arent, there will be no bubbles of oxygen produced