Chemistry Sodium Thiosulpahte

Introduction

Over the next few weeks I will be doing several attempts of the same experiment that involves the reaction of sodium thiosulphate and hydrochloric acid, I will be closely watching the reaction and how long in takes for the reactants to react. As yet I have not decided which of the several variables I will be changing. I also aim to take results of the reaction down onto a table, which then will be transferred onto a line graph, which will show us the nature of the reaction.

Variables

There are five factors which affect the rate of a reaction, according to the collision theory: temperature, concentration (of solution), pressure (in gases), surface are (of solid reactants), and catalysts. I have chosen to investigate the effect of temperature on the reactants.

Aim

To see the effects of a change in temperature and concentration we affect the rate of the reaction. The reaction that will be used is:

Sodium Thiosulphate + Hydrochloric Acid

Na2S2O3 (aq) + 2HCl (aq).

Plan

I am going to investigate what happens when sodium thiosulphate and Hydrochloric acid react.

As I have done this experiment before I have a good understanding of what I need to so hopefully nothing will go wrong, also I will be going back to results and information I used before the experiment to make sure I am doing everything right.

As I want to have a fair test, so that I get accurate results, I will make sure that all the main variables will stay the same all the way through the experiment, concentration of both solutions will be kept constant, as there is no gas the variable of pressure wont have an affect on this reaction, as I am using no solids the variable of suface area wont be a problem, and finally as I am not using a catalyst it wont have an effect on the reaction. As well as these things being important there is a more important aspect that I will need to take into account and that is my own safety, and the safety of my fellow pupils. To make sure I don't endanger myself I will be using the following apparatus:

1 thermometer

1 beaker

2 measuring cylinders

1 conical flask

1 tripod

1 gauze

1 heatproof mat

1 stopwatch

1 Bunsen burner

1 pair of tongs

1 pair of goggles

To make it easy to follow when drawing graphs and when logging my data I will be using a table similar to this:

As I have shown above I will be taking five different results, but I have also decided to repeat the experiment three times so that if I get any anomalous results then they will be discounted.

Volume of 1m sodium thiosulphate (ml) Volume of 1m hydrochloric acid Tempreature Time until

X disappeares

1 10 10 30

2 10 10 40

3 10 10 50

4 10 10 60

5 10 10 70

Method

HCl and sodium thiosulphate are poured out into two measuring cylinders. A beaker is half filled with water from a tap. The water is placed on top of a Bunsen on a blue flame and the two measuring placed inside the water bath. The water is heated to the necessary temperature (30Ñ"C to 70Ñ"C) then the two measuring cylinders are taken out and the contents of both are poured into a conical cylinder. The time it takes for the X to disappear is timed and recorded. The experiment is repeated using all the temperatures. The entire procedure is the repeated.

Repeat results and averages will be taken to improve the credibility of the findings, and present solid grounding for the final conclusion. The repeat results will help get rid of any anomalies and the average will give a good summary of the results of the experiment.

Prediction

I predict that as the temperature is increased the rate of reaction will increase. This means that the graph drawn up in my analysis will have positive correlation, and will probably be curved, as the increase in rate of reaction will not be exactly the same as the temperature is increased. This can be justified by relating to the collision theory. When the temperature is increased the particles will have more energy which means they will move faster. Therefore they will collide more often and with more energy. Particles with more energy are more likely to overcome the activation energy barrier, which means they will react successfully.

Collision theory:

For a reaction to occur particles have to collide with each other. Only a small percent result in a reaction. This is due to the energy barrier, which needs to be overcome if a reaction is to take place. Only particles with enough energy to overcome the barrier will react after colliding. The minimum energy that a particle must have to overcome the barrier is called the activation energy. The size of this activation energy is different for different reactions. If the frequency of collisions is increased the rate of reaction will increase. However the percent of successful collisions remains the same. An increase in the frequency of collisions can be achieved

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