Rates of reaction

Question 1

How is the rate of reaction defined?

Answer 1

The amount of reactant used up, or product formed in a given time period

Question 2

How to find the mean rate of reaction?

Answer 2

mean rate of reaction = quantity of reactant used / time taken
or
mean rate of reaction = quantity of product formed / time taken

Question 3

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

Answer 3

Particles have more energy so they move around faster. This makes them collide more frequently and with more energy so there are more successful collisions each second. This means there will be a lower activation energy level so the reaction is faster. `

Question 4

What is the effect of increasing concentration/pressure on rate of reaction?

Answer 4

If the pressure of gaseous reactants are increased there are more reactant particles for a given volume. This means there will be more successful collisions and so the rate of reaction increases.

Question 5

What is the effect of increasing surface area on rate of reaction?

Answer 5

If the surface area of a reactant is increased more particles are exposed to the other reactant, which leads to more successful collisions per second. Th activation energy levels decreases and the rate of reaction increases.

Question 6

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

Answer 6

It provides an alternate route for the reaction which lowers the activation energy. Allowing the rate of reaction to increase

Question 7

How to measure the effect of changing the temperature on the rate of a reaction by the mass change?

Answer 7

1. Add a set volume of dilute hydrochloric acid to a conical flask and carefully place on a mass balance
   2) Add some magnesium ribbon to the acid and quickly plug the flask with cotton wool
   3) start the stopwatch and record the mass on the balance. Take readings at regular intervals
   4) Plot the results in a table and work out the mass list from each reading
   5) repeat with more concentrated solutions.

Question 8

What does the cotton ball do?

Answer 8

Lets gas escape but stops acid from spitting

Question 9

How to measure change in rate of reaction using color change?

Answer 9

1) Add a set volume of dilute sodium thiosulfate to a conical flask
2) Place the flask on a piece of paper with a black cross drawn on if. Add some dilute HCI fo the flask and start the stopwatch
3) Now watch the black cross disappear through the cloudy sulfur and time how long it takes to go.
4) The reaction can be repeated with solutions of either reactant at different concentration. The depth of the liquid must be the same each time
5) The higher the concentration the faster the rate of reaction.