Rates Of Reactions

Question 1

What is collision theory?

Answer 1

Reactions depend on the frequency of the collisions and the energy with which they collide. The more collisions the faster a reaction is and particles must collide with enough energy for a collision to be successful.

Question 2

What is the activation energy?

Answer 2

The minimum amount of energy that particles need to react. They need this energy to break the bonds and start the reactions. The greater the activation energy, the more energy needed to start the reaction.

Question 3

What does the rate of reaction depend on?

Answer 3

Temperature, concentration of a solution, pressure of a gas, surface area and the presence of a catalyst.

Question 4

Why does temperature increase the rate of reaction?

Answer 4

The particles have more kinetic energy and move faster so have more frequent and forceful collisions, resulting in more successful collisions and hence a faster rate of reaction.

Question 5

Why does concentration or pressure increase the rate of reaction?

Answer 5

More particles in the same volume, so collisions more frequent so increased rate of reaction.

Question 6

How does increased surface area increase rate of reaction?

Answer 6

Increased surface area to volume ratio, more area to collide with, so frequency of collisions will increase

Question 7

How does a catalyst increase rate of reaction?

Answer 7

A catalyst provides an alternative pathway of lower activation energy, and is not chemically changed or used up in the reaction.

Question 8

Investigating the effect of surface area on rate of reaction

Answer 8

1. Add marble chips to dilute HCl in a conical flask, with a delivery tube and gas syringe attached to the top
2. Measure the volume of gas produced on the gas syringe every 30 seconds and record results in table
3. Plot graph of results
4. Repeat experiment with same vol and conc of acid and same mass of calcium carbonate powder
   Can also change this to be conc of acid

Question 9

Investigate effect of temperature on rate of reaction

Answer 9

1. Sodium thiosulfate and HCl are both clear, but react together to form yellow precipitate of sulfur
2. Do a black cross on a piece of paper and place it under conical flask
3. Measure the rate by watching cross disappear and timing it
4. Repeat for solutions at different temperatures, use a water bath to heat solutions before mixing
5. Keep vol and conc of liquids same

Question 10

Investigate the effect of catalysts on rate of reaction

Answer 10

1. Add hydrogen peroxide and catalyst, manganese (IV) oxide to conical flask and attach gas syringe and delivery tube
2. Measure the volume of gas produced every 30 seconds
3. Repeat experiment with same vol and conc of hydrogen peroxide but same mass of different catalyst, e.g. copper oxide