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An investigation into the factors affecting the rate of a reactio...

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An investigation into the factors affecting the rate of a reaction: The write up of an experiment using Sodium Thiosulphate and hydrochloric acid

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Skill Area P: Planning

What I going to investigate is how different factors affect the rate of the chemical reaction of Sodium Thiosulphate and Hydrochloric acid. In which a precipitate is formed and causes the solution to become opaque. They react as in the equation below:

Sodium Thiosulphate + hydrochloric acid -->; sodium chloride + sulphur + sulphur

dioxide+

Water

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

I plan to change the concentration of the Sodium Thiosulphate by diluting it with water but I plan to keep the same volume of liquid in the beaker to ensure that it is a fair test because the volume of liquid in the beaker may affect the reaction time. Also in order to make it a fair test I am going to keep the following variables the same: the temperature; the volume of the hydrochloric acid; the same distance between the light sensor and the solution; the same distance from the light source and the solution; the voltage going into the light bulb; same concentration of acid; same beaker and apparatus; and the same total volume.

I have identified the following hazards and I will deal with them as shown below:

Hazard 1: Dealing with Acids -- I will wear safety specs to protect my eyes and care will be taken while handling the acid.

Hazard 2: Electrical Equipment - I will not touch the electrical equipment while handling liquids and care will be taken to make sure that all electrical equipment will not come into contact with liquids.

METHOD

Equipment:

A beaker

Computer

Lab-Pak

Light Source (I used a 6V bulb)(Surround the light with a ring of black cardboard to focus the light

Light sensor (again surround the sensor with black cardboard to irradiate light from other sources)

Syringe

Burette

Clamp stand

Sodium Thiosulphate

Hydrochloric Acid

Firstly I set the computer up and loaded the software, which I used to record the data. I then attached the light sensor onto the clamp...