Iron (III) Chloride Concentration and Copper Mass Loss

The aim of my investigation is to study the effect of the rate at which copper is fixed by different concentrations of Iron (III) Chloride. I will place copper strips in varying concentrations of Iron (III) Chloride, and then record results and interpret them.

The reaction above is used in technology. Printed Circuit Boards are thin, flat boards made from non-conduction materials eg.plastic. Chips and other components are mounted on to them. The PCB starts off as a sheet of plastic coated with a layer of copper.

It is placed into a tank containing a concentrated solution of Iron (III) Chloride to remove the excess copper and the protected copper, which remains become the PCB tracks.

This is the formulae of the reaction which takes place between copper and Fe3+ ions shown below:

Cu (s) + 2Fe3+ (aq) Cu2+ (aq) +2Fe2+ (aq)

It is a REDOX reaction. This means that the copper is reduced as it has lost 2 electrons. It becomes a Cu2+ ion .

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The iron is oxidised, as it has gained 2 electrons and therefore it becomes a Fe2+ ion as demonstrated below.

Cu - 2e- Cu2+ Fe3+ + e- Fe2+

I have studied kinetics in detail. And I have 6 different experiments which can all be related to our coursework.

I. Magnesium ribbon and various concentrations of Hydrochloric acid

II. Hydrogen peroxide and Manganese Dioxide

III. Sodium Thiosulphate and Dilute Hydrochloric acid

IV. Calcium carbonate and Dilute Hydrochloric acid

V. Barium Chloride and Sodium Sulphate

VI. Glucose solution and Acidified Potassium Permanganate Solution

From doing these experiments I learnt that there are 4 main factors that affect the rate of reaction.

They are;

* Concentration of a reactant in solution or in the gas state

* The higher the concentration of the reactant the faster the process will occur. In the kinetics practical of magnesium ribbon and various concentrations of hydrochloric acid we discovered that as the concentration of Hydrochloric acid increased, the faster the magnesium was dissolved. Therefore the reaction rate was greatly influenced by the concentration of the reactant.

* Temperature

* The higher the temperature the faster the reaction will happen. In the kinetics experiment between the Glucose solution and Acidified Potassium Permanganate solution, two solutions were composed in test tubes and one was left in room temperature, while the other was left in a bath of hot water. We found that the one in the hot water bath turned colourless quicker than the other one which therefore goes to prove that temperature greatly influences the reaction rate. Read the answer what is the optimum concentration of pectinase

* 3) Surface area of reactant

* The larger the surface area; the faster the reaction rate. In the calcium carbonate and hydrochloric acid kinetics practical we found that the larger the surface area of the calcium carbonate lumps, the faster the reaction occurred which therefore is evidence that the surface area greatly influences the rate of reaction.

* 4) Presence of a Catalyst-

* A Catalyst is a substance which increases the rate of a reaction without being consumed in the process. We learn of this aspect from the last experiment between Hydrogen Peroxide and Manganese Dioxide. The manganese Dioxide speeds up the reaction without being consumed in the process. Consequently, the presence of a catalyst affects the rate of reaction.

* The kinetics experiment most similar to ours is the reaction between Magnesium Ribbon and various concentrations of Hydrochloric Acid.

* We placed the Magnesium into the various solutions of Hydrochloric acid and timed how long it took for the reactions to finish. This meant that the magnesium ribbon could no longer be seen. We discovered that as the concentration of the hydrochloric acid increased, the faster the reaction occurred and therefore the more concentrated the solution is, the faster the reaction will occur.

Before investigating the effect of changing the concentration of the Iron (III) Chloride upon the rate of reaction with the copper there were some variables that had to be taken in to account.

* Independent variable - This is the variable which we will change i.e the concentration of the Iron (III) Chloride solution. 5 solutions of concentrations 2M, 1.6M, 1.2M, 0.8M and 0.4M will be used. They are spread over a wide range so as to give rise to noticeable changes in the mass loss of copper from which we can interpret effectively.

* Dependant variable - This is what we will be measuring i.e the rate of reaction measured as the change in mass of the copper strips which are removed from the Iron (III) Chloride solution after 5 minutes. The reason 5 minutes is used for each experiment is that it will highlight any significant mass losses and therefore this proved to be sufficient enough time for the process to occur.

Controlled variables

We have to control these in order to ensure a fair test:

Same level of solution in all test tubes - this is to ensure the same surface area of copper exposed is kept constant in each experiment as the surface area affects the rate of reaction. To control this we will measure 30cm3 of solution per test tube to ensure a fair test. We ensured that we used the same volume of solution each time by marking each test tube at the same height, and filling it with solution to exactly that mark. This made sure that the same area of copper was being reacted with each test.

Constant temperature throughout experiment

The higher the temperature the higher the reaction rate. Therefore as this is a factor which greatly influences the rate of the reaction we will control it by doing the experiment at room temperature in as short a time as possible to not give rise to changes in temperature which would make it an unfair test. We know that temperature is a great influence from the previous experiments we done with Acidified Potassium Permanganate Solution and glucose solution. The solution was put into two separate test tubes and one was placed into a warm water bath. We observed that the one placed in the water bath turned colourless more quickly than the one in open air. Therefore, temperature is definitely a factor in reaction rate.

Prediction

I believe that the more concentrated the Iron (III) Chloride solution becomes, then the more copper will react in 5minutes. I am suggesting this because when I completed the Magnesium and Hydrochloric acid kinetics experiment, I observed that as the concentration of the HCL increased; the rate at which the magnesium dissolved also increased. Therefore, I think the same will happen with the Iron (III) Chloride and copper.

Apparatus

To complete the experiment I will need the following apparatus.

o a strip of copper

o A ruler

o A scriber and scissors to cut the strip

o Two burettes (one with 2M chloride and one with distilled water.)

o A test tube to hold the solutions

o A flushing beaker to flush out the solution

o A squeeze bottle to clean the copper strip of the solution and stop the reaction.

o A stop clock- to time the reaction.

o A test tube to carry out the experiment

o A balance to measure the mass of the strip of copper

o A small beaker to mix each dilution

o A bottle of iron chloride

o A bottle of distilled water

In order for me to successfully complete the experiment, I will need to:

* Measure and cut the strip of copper.

* Weigh the piece of copper, for the initial mass

* Set up two burettes, on with iron chloride, and the other with distilled water.

* Put 50cm of iron chloride into the test tube.

* Add strip of copper into the beaker

* Start timing

* After 5mins has passed take the strip out and clean it with the squeezy bottle.

* Dry the copper and weigh it

* Repeat steps 4-8 varying the concentration of iron chloride each time by taking of 10cm from original and adding 10cm of distilled water each time.

Reactants

1. Iron (III) Chloride solution- I will use 5 different solutions of this. The varied concentrations are 2M, 1.6M, 1.2M, 0.8M and 0.4M.

2. Distilled Water- This will vary the concentrations of my Iron (III) Chloride solution.

Method

1) You need to measure your copper strip, and then cut it to the appropriate size.

2) Find out and record the weight of the copper strips.

3) Make the first solution and divide equally among the 2 test tubes

4) Drop copper into solution, in unison start the clock.

5) Leave the copper in the solution for 5minutes.

6) When the 5minutes is up, take the copper out immediately.

7) Rinse the copper strip carefully; removing all the solution so there is no extra weight.

8) Dry using paper towels to get rid of all excess water.

9) Re-weigh the copper strip and record correct mass

10) Clean beaker and test tubes, ready for the next experiment.

11) Then repeat the experiments using the other concentrations.

We will take 2 readings for each molar value and we will then find an average of these to make the results more accurate and to ensure a fair test. We will also ensure the temperature is constant throughout the whole experiment, each solution is at the same level in the test tube and the reaction occurs for exactly 5 minutes each time

For Safety

* Place chairs neatly under desks.

* Tie hair back and keep sleeves tucked in.

* Wear safety goggles to protect eyes.

* Take care to avoid skin contact with Iron (III) Chloride as it is an irritant.

* Wipe up spillages immediately.

* Take care with copper based solutions as they are reasonably toxic.

* Wash hands after practical, especially before eating.

Strategy for Dealing with Results.

I will use the following concentrations of Iron Chloride and the measurements below are what I will use in my experiment.

Concentration (M)

Volume of 2M FeCl3

Water (cm3)

2

50

0

1.6

40

10

1.2

30

20

0.8

20

30

0.4

10

40

After I complete my different investigations, I will have to record them in a suitable table. I have decided to display my results in a table like the one below.

Concentration of FeCl3 (M)

1st mass of strip of Cu (g)

2nd mass of strip of Cu (g)

Change in mass (g)

2

1.6

1.2

0.8

0.4

To work out the mass change, I simply have to use the following formula;

1st mass of strip - 2nd mass of strip = change in mass.

To calculate the average change in mass between the two sets of results, I will use the following formula. I will repeat this for all my different concentrations of Iron Chloride.

1st Change in Mass (g) + 2nd Change in Mass (g) = Average Change in Mass (g)

2

I predict that the graph I will construct will look like this.

It will be a graph of rate of reaction against concentration of iron (III) Chloride.

The above graph shows that the rate of reaction is directly proportional to the concentration (M) of Iron (III) Chloride. Again, this shows that as the concentration increases, the rate of reaction does too.

Obtaining Evidence

These are the results I recorded for my experiments. I have two sets of results, from the other half of my group. This will further any predictions I make and will cause my results to be more reliable, if two sets coincide with each other.

Experiment 1

Concentration of FeCl3 (M)

1st mass of strip of Cu (g)

2nd mass of strip of Cu (g)

Change in mass (g)

2

1.790

1.617

0.173

1.6

1.617

1.465

0.152

1.2

1.465

1.360

0.105

0.8

1.360

1.291

0.069

0.4

1.291

1.260

0.031

I calculated the change in mass by using the formula Original Mass (g) - New Mass (g) = Change in Mass (g)

E.g. 1.790g-1.617= 0.173g

Therefore the change in mass is 0.173g

Experiment 2

Concentration of FeCl3 (M)

1st mass of strip of Cu (g)

2nd mass of strip of Cu (g)

Change in mass (g)

2

1.6

1.2

0.8

0.4

This table represents the average mass loss (g) for each concentration.

Concentration (M)

Average mass loss (g)

2

1.6

1.2

0.8

0.4

Reliability of Results

I believe that my results are quite reliable. As you can see, both sets of results correspond with each other. During the experiments, we used the appropriate equipment and worked to the best of our ability to keep inaccuracies at bay. We dried the strips carefully so no extra water was recorded on the scales.

Interpretation

The chart on the previous page is the graph I constructed from my table of results. It confirms my earlier prediction, that the rate of mass loss is directly proportional to the concentration of Fe(III)Cl. As you can see, as the concentration increases, so too, does the mass loss. I think this is because there are more collisions happening with Iron Chloride and copper particles. If the concentration is greater, then more ions are present hence more collisions. Consequently, a faster reaction rate.

Evaluation

When I completed my graph, I realised that I did not have any anomalous results. I feel this is because we used accurate measures and followed the method meticulously. However as in all experiments, there were things that could be improved.

* I realised that we had cut our strips from the same sheet of copper to a standard size. Our aim was to create identical strips so as to ensure a fair test but when we weighed the strips, they were different weights, which means that they were not exactly the same size and so did not have exactly the same surface area.

* Another problem is cross-contamination of the test tube. If some of the previous solution remains in the test tube, then the next solution could be affected and the change in mass will be greater or less than it should be.

* I also think that perhaps, the two strips of copper were not put in at the exact same time therefore this could cause anomalies.

In conclusion, I have realised that my theory was in fact correct. The concentration of a solution plays a very important role in the rate of reaction as they are directly proportional to each other.