Investigating Rates of Chemical Reactions

Investigating Rates of Chemical Reactions

Planning.

Introduction

============

I am going to investigate how increasing the concentration of a

substance affects the rate of reaction. I will be studying how

increasing the concentration of Sulphuric acid affects the rate of

reaction when added to Magnesium. The equation for this is:

Magnesium + Sulphuric Acid ® Magnesium Sulphate + Hydrogen

Mg (s) + H2SO4 (aq) ® MgSO4 (aq) + H2

Background Knowledge

====================

There are many factors that affect the rate of a reaction; these

include temperature, concentration, catalysts and surface area. In my

preliminary investigation I used the reaction between Sodium

Thiosulphate Solution and dilute Hydrochloric Acid to study the effect

of temperature on rate. When I mixed the reactants the solution went

cloudy and eventually I couldn't see a cross on a piece of paper under

the reaction vessel. I timed how long this took, then increased the

temperature by 10°c and carried out the same experiment. I have given

my results table below:

Temperature (°c)

Time taken for cross to disappear (seconds)

20 (21)

113

30 (33)

57

40 (42)

28

50 (50)

12

This shows that by increasing the temperature by 10°c the rate of

reaction gradually increases. I will explain this by using the

collision theory. All acids contain hydrogen so when you dissolve them

in water they dissosciate and hydrogen ions are produced. A reaction

between particles will only take place if there is a head-on

collision, more collisions means a faster reaction. When the

temperature is increased the particles are given more energy so move

faster and more head-on collisions wilo therefore take place.

Prediction

==========

I predict that as I increase the sulphuric acid the rate of reaction

will increase. I think this will happen because as I increase the

concentration I am increasing the amount of particles in the vessel.

If there are more particles there is a higher probability of head on