Rates of Reaction

Rates of Reaction

Prediction

(Na2 S2 O3 + 2HCL ---> 2NaCl + SO2 + S + H2O)

This is the equation for Sodium Thiosulphate reacting with 2 Molar of

Hydrochloric Acid. There are a number of variables in the experiment

which must be controlled in order for the experiment to be a fair

test.

These include temperature, which must be kept constant throughout the

experiment or the results would not match. The experiment will be

performed at room temperature (Around 25 degrees). Another variable is

volume of Hydrochloric acid, which must be kept the same as well. For

this experiment, I will be using 5cm of HCL. If all of these variables

are controlled, then the experiment will be a fair test. However,

there will be a degree of human error because there is no definate

point at which the cross disappears, it relies on human judgement.

My prediction is that as the concentration of Sodium Thiosulphate

decreases, the rate of reaction will decrease accordingly and the

reaction will take longer to complete. This is the basic principle of

the Particle Theory. The particle theory is that if there are less

atoms to 'collide' into each other and react, then the reaction will

be slower than if there were more atoms to collide.

Therefore, if the concentration, so number of atoms if lower, then the

amount of collisions between Sodium Thiosulphate and Hydrochloric Acid

will be less frequent. Also, when the concentration of Sodium

Thiosulphate is higher, the water will get cloudy faster due to the

fact that there will be less water available to disrupt the reaction.

[IMAGE]

As the reaction takes place, the amount of Hydrochloric Acid and

Sodium Thiosulphate decreases, which therefore decreases the

probability of the two atoms hitting each other, reacting. The

reaction will slow down, because if two Thiosulphate atoms or two HCL

atoms collide, then nothing will happen. This is the particle theory.

Method

Equipment

· Beakers

· Measuring cylinders