Rates Of Reaction Essay Research Paper Contents

Rates Of Reaction Essay, Research Paper

Contents Page

Page Title

1 Planning

2 Method and prediction

3 Diagram

4 Results for temperature and concentration on Tables

5 Graph for results for rate of reaction against temperature

6 Graph of results for rate of reaction against time

7 Graph for concentration results

8 Graph and table of typical results

9 Conclusion and Evaluation…

10 End of evaluation

This investigation is about Rates of Reaction and what affects them. In this case I am going to look at hydrochloric acid and sodium thiosulphate, which is a precipitation reaction. I will be investigating whether a change in temperature affects the rate of reaction.

(Planning)

Sodium thiosulphate and hydrochloric acid react together to produce sodium chloride, sulphur dioxide, water and sulphur. This is also shown in the word and symbol equations below:

Word:

Sodium thiosulphate + Hydrochloric acid . Sodium chloride + sulphur dioxide + water + sulphur

Symbol:

Na2S2O3(aq) + 2HCl(aq) -* 2NaCl(aq) + S(s) + SO2(g) + H2O(l)

Both of these solutions are colourless. They react to produce a solid (sulphur, which is the yellow precipitate), and as it cannot dissolve in water, the solution will become cloudy.

A reaction will only occur where the particles of the reactants meet and combine. This is called the collision theory. Therefore it stands to reason that to increase the rate of reaction it is necessary to cause more particles to collide harder and make it happen more often. There are several ways to do this and these make up the variables for this experiment.

1) Increasing the temperature — Increasing the temperature of the reactants will provide the particles with more kinetic (movement) energy. This will make the particles move faster. The number of successful collisions per second will also increase; hence the rate of the reaction increases. More collisions have an energy greater than the activation energy. But, although the rate of reaction is increased, the amount of the products produced at the end will remain the same (this is a continuous, independent variable, which I will be testing).

2) Adding a catalyst — a positive catalyst will speed up a reaction. The catalyst provides surfaces, which the molecules stick to, and react upon. It also lowers the activation energy, which is the energy needed for bonds to be broken, and the reaction to occur) by reducing the initial energy needed. This increases the number of successful collisions, resulting in an increased rate of reaction. Catalysts are specific to certain reactions.

3) Increasing the surface area — This involves .breaking up. the reactant into smaller pieces. It provides more opportunities for the particles to collide (for example, the reaction between calcium carbonate and hydrochloric acid. When the calcium carbonate is powdered, there is more of it in contact with the hydrochloric acid). In some cases, stirring also has the same affect.

4) Increasing the concentration — A more concentrated solution will contain more of the same particles, which will be more tightly packed. So, once again, there will be a much greater chance of successful collisions between the particles (In this case, this reaction is exothermic, as it gives out energy)

(Method)

I will be using:

A kettle

A beaker

A thermometer

A timer

Sodium thiosulphate

Hydrochloric acid

A conical flask

A piece of paper

A black marker

A window (as a light source)

A pipette

I shall set up the equipment as in the diagram on page 3, drawing a black cross on a piece of paper with the marker. I shall then fill the kettle with water, and heat the water, to the testing temperatures. I will place the 5cm. of Hydrochloric acid into a 50ml conical flask. When the temperature is correct (20, 30, 40, 50 and 60 degrees centigrade), I shall then add 25cm. of a mixture of sodium thiosulphate and water (the concentration of the sodium thiosulphate will be 0.25 molars, and this will remain constant during the experiment). Simultaneously, I will start the timer. I shall test each temperature two times and then take an average to ensure that the result is balanced and not just a result of a fluke. The results will be taken optically, as we do not have the chance to use a computer. I will keep the timer on until the black cross marked on the piece of paper has disappeared. To ensure my results are as accurate as possible, we will use a pipette to measure the sodium thiosulphate, when placing it in the beaker. I will try to keep my measurements as precise as possible.

(My Diagram for the experiment is on Page 3)

I will have to consider safety precautions, so I will wear goggles, and tie my hair back to prevent any hazards. I will also have to make sure the apparatus is stable.

I will obtain results from the other choice of experiments, which is on the variable of concentration.

I will also obtain .typical results., to compare my results.

(Prediction)

I predict that temperature is proportional to rate of reaction. I say this due to my research on the collision theory, et

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