Introduction
In this experiment I produced chlorine by using electrolysis. Electrolysis is chemical decomposition produced by passing an electric current through a liquid or solution containing ions. It was discovered by an English scientist named Michael Faraday in 1834. We all know that water is made up of 2 positive hydrogen atoms and 1negative oxygen atom; by using electrolysis we can split these atoms. Since water itself is not a good conductor of electricity, an electrolyte needs to be added. Salt is perfect for this. During electrolysis the chlorine collects at the anode (positive electrode) and hydrogen collects at the cathode (negative electrode) and a solution of sodium hydroxide (NaOH) forms. Oxidation happens at the anode because electrons are lost. Reduction happens at the cathode because electrons are gained. The formula that would be achieved would look like this:
NaCl + H20 ~> Cl + 2H + NaO.
Aim
To produce chlorine by electrolysis of salt water and pool acid
Investigative Question
How many grams of salt would be needed to produce the same amount of chlorine as 10ml pool acid?
Hypothesis
Chlorine will be produced by electrolysis of salt water and pool acid
Variables
Independent: The % of salt water or hydrochloric acid added
Dependent: The color on the indicator
Controlled: The strength of the hydrochloric acid, the volume of the experiment i.e. size of container, time, distance between rods, volume of water
Method
‘ Apparatus:
o battery charger
o 2x carbon rods
o Pool acid (50% HCl)
o Salt
o Teaspoon (1 spoon= 5g)
o Measuring jug
o Scale
o 2x containers
o Chlorine testing slips
‘ Filled jug with 1L water
‘ Poured water into container and repeated with second container
‘ 30ml pool acid added to first container
‘ Tested chlorine level before electrolysis by adding chlorine testing slip to solution. Result: 0ppm(parts per million) chlorine present
‘ Inserted carbon rods with + and ‘ charges into solution
‘ Plugged in battery charger
‘ Left rods in solution for 2 minutes of electrolysis
‘ Tested for solution for chlorine with chlorine test strips by holding slip in solution for +/- 15 seconds. Results: 15ml of pool acid diluted in 1L of water produced 10ppm of chlorine at 2 minutes of electrolysis.
‘ Repeated test with 15ml pool acid diluted in 1L of water with electrolysis for 1 minute
‘ Results: 5.5ppm of chlorine produced from 15ml pool acid with electrolysis for 1 minute
‘ Repeated test with 10ml pool acid
‘ Electrolysis of 10 ml pool acid diluted in 1L of water produced 5ppm of chlorine per 10ml
‘ Repeated test with 5ml pool acid
‘ Results: 4.5ppm of chlorine produced.
‘ Moved on to second container. Dissolved 5g of iodated table salt into 1L of water
‘ Tested chlorine of salt solution. Result: 0ppm of chlorine present
‘ Repeated electrolysis test with salt solution using constant variables
‘ 5g salt diluted in 1L water with electrolysis for 1 minute produced 0.75ppm of chlorine
‘ Repeated test using 10g salt
‘ Test results produced 1.5ppm of chlorine
‘ Based on above results it is concluded that chlorine is produced at 0.75ppm per 5g of salt added to solution, therefore,
‘ Predicted possible outcome for next test by using the formula 5ppm / 0.75ppm x 5g= 33g
‘ Repeated test with the concentration from prediction (33g)results produced 5ppm of chlorine which proved the above statement and answered the investigative question
Safety precautions
‘ Hydrochloric acid is highly corrosive and very dangerous. Always handle it with care. If accidental contact occurs seek medical help immediately.
‘ Chlorine gas is poisonous and should not be inhaled. If accidental inhalation occurs seek medical help immediately.
‘ Hydrogen gas is highly flammable and explosive. Avoid bringing any flame near the experiment. Do not smoke near the experiment.
Data
Pool acid
Test number Concentration (ml) Electrolysis time (minutes) Chlorine produced (ppm)
T1 30 0 0
T2 30 2 10
T3 15 1 5.5
T4 10 1 5
T5 5 1 4.5
Salt
Test number Concentration (g) Electrolysis time (minutes) Chlorine Produced (ppm)
T1 5 0 0
T2 5 1 0.75
T3 10 1 1.5
T4 15 1 2.25
T5 33 1 5
Analysis
Discussion
In this experiment I produced chlorine by using electrolysis of salt water and pool acid (50% HCl). I filled 2 containers with 1L water in each. In one container I put 30ml pool acid into the water and used a chlorine testing slip to check if there were any traces of chlorine in the solution; the result was that there was no chlorine. Next I placed the 2 carbon rods into the solution and turned the battery charger on. After 2 minutes I removed the rods and checked if there was any chlorine in the solution, my result this time was that there was 10ppm (parts per minute) of chlorine in the solution which meant that the experiment worked and I could make chlorine with electrolysis of pool acid. I repeated the experiment with 15ml pool acid for 1 minute of electrolysis. My results were that 5.5ppm chlorine was produced. I repeated the experiment with 10ml of pool acid and for 1 minute of electrolysis. My results were that 5ppm of chlorine was produced. I used this data in my investigation. I repeated the test again with 5ml pool acid and my result was 4.5ppm chlorine produced.
I then moved on to the second container and added 1 teaspoon (5g) of salt into the solution. I then checked for chlorine and there were no traces of it in the solution. I placed the rods in the solution and waited a minute before removing them. The result was that there was 0.75ppm of chlorine in the solution and that the experiment worked. I repeated the experiment with 10g of salt and got 1.5ppm of chlorine from it. I repeated again with 15g and got 2.25ppm of chlorine from it. After these tests I noticed that the difference between each test was 0.75ppm/5g. I decided to attempt to predict the results of my next experiment by using the formula 5/ 0.75x 5=33 ‘I got the first value from the value I wanted to reach, the second value from the difference between tests and the last value from the value I used to increase the concentration of salt- I then repeated the test with the value I got from the formula and my results were that there was 5ppm of chlorine in the solution. This provided the answer to my investigative question. It takes 33g of salt to make the same amount of chlorine as 10ml of pool acid.
Conclusion
It is concluded that my hypothesis was correct, chlorine can be made by electrolysis of salt water and pool acid, and the results from my experiments answered my investigative question.
Application
Electrolysis of salt water can benefit communities by providing a cheaper means of chlorine which can be made at home which would convenience a great deal of people.
It can be used for purification of polluted water because it kills off bacteria and cleans the water.
Besides producing hydrogen, the electrolysis of water also produces oxygen. In nuclear submarines, seawater is electrolyzed to generate oxygen for the crew to be able to breathe while remaining under water for long periods of time. Likewise, space stations can use electrolysis to produce oxygen from wastewater or from surplus water made by fuel cells.
The products of the electrolysis of salt solution have important uses in the chemical industry:
‘ Hydrogen is used in the manufacture of ammonia and margarine (it is used to harden vegetable oils).
‘ Chlorine is used to:
‘ Kill bacteria in drinking water and swimming pool water
‘ Make solvents
‘ Make plastics such as polyvinyl chloride (PVC)
‘ Make household bleach.
‘ Sodium hydroxide is used to make soap and household bleach.
Bibliography
http://www.newworldencyclopedia.org/entry/Electrolysis
http://www.docbrown.info/page01/ExIndChem/electrochemistry03.htm
http://www.bbc.co.uk/schools/gcsebitesize/science/ocr_gateway/chemical_resources/sodium_chloride.shtml
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