Inorganic chemistry Displacement Reactions of Halogens lab PDF

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Laboratory activity on the displacement reactions of halogens. This lab is done using the halogens, Fluorine, Chlorine and Iodine....

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NATALIA NOYES DUE DATE: 25/02/21 Displacement Reactions of Halogens

Aims: You will use displacement reactions to work out a reactivity series for chlorine, bromine and iodine. Remember that a more reactive halogen will displace a less reactive halogen from its compounds in solution.

Apparatus: Goggles,Test tube ,Test tube rack ,Teat pipettes ,0.2M potassium chloride solution 0.2M potassium bromide solution , 0.2M potassium iodide solution ,chlorine water ,bromine water, iodine water

Method: 1. About 1cm3 (about half a pipette-full) of potassium bromide solution was added to the test tube. 2. One drop of chlorine water was added, and the test tube was shaken gently to mix the contents. 3. If a colour change was seen, a note of it was made in a table. If a colour change was not seen, up to 9 more drops of chlorine water were added (remembering to shake the test tube after each drop) and a note of any colour change was made in the table. If a colour change still was not seen, ‘No reaction’ was written in the table. 4. The test tube was washed out. 5. Steps 2 – 5 were repeated for each of the following combinations: chlorine water added to potassium iodide bromine water added to potassium chloride bromine water added to potassium iodide iodine water added to potassium chloride iodine water added to potassium bromide

Results: TABLE SHOWING COLOUR CHANGES IN THE DISPLACEMENT REACTIONS OF HALIDES. Number of reactions

Potassium Iodide

Potassium Bromide

Potassium Chloride

2

Reddish brown

Yellowish orange

No reaction

Chlorine water

1

Orange brown

No reaction

No reaction

Bromine water

0

No reaction

No reaction

No reaction

Iodine water

Analysis: Amongst the three halogens used in this experiment -chlorine, bromine, and iodine -Chlorine seems to be the most reactive of the three. This was deduced as the chlorine was able to displace iodide and bromide from its solutions, whilst bromine was only able to displace iodide from its solution and iodine was not able to displace neither chlorine nor bromine. Therefore, the order of reactivity of these halogens can be observed below: Decrease in reactivity

Chlorine Bromine Iodine

The reason why these halogens decrease in reactivity as you go down the group is due to the decrease in the ease at which that halogen can attract an electron towards itself to attain stability (a full valence shell). Hence why the higher up the group a halogen is, the more reactive it will be as it is easier for it to attract an electron than those halogens which are found below it. The ease at which a halogen can attract an electron to attain stability decreases down the group as the atoms of each successive halogen gets bigger, thus, there being much more shielding between the nucleus and the valence electrons, which in turn means that the electrostatic forces

of attractions that exist amongst the nucleus and valence electrons also decreases, making it harder for the halogen to gain an electron.

If fluorine water and potassium fluoride where in the experiment, the results that would be produced might look as follows: TABLE SHOWING COLOUR CHANGES IN THE DISPLACEMENT REACTIONS OF HALIDES. Number of reactions

Potassium Iodide

Potassium Bromide

Potassium Chloride

Potassium Fluoride

3

Reddish brown

Yellowish orange

Yellow

No reaction

Fluorine water

2

Reddish brown

Yellowish orange

No reaction

No reaction

Chlorine water

1

Orange brown

No reaction

No reaction

No reaction

Bromine water

0

No reaction

No reaction

No reaction

No reaction

Iodine water

In this case, the most reactive halogen would be Fluorine.

Word and symbol equations for each of the reactions seen in this experiment are below: Chlorine + potassium bromide  potassium chloride + bromine Cl2(aq) + 2KBr(aq)  2KCl(aq) + Br2(aq) Chlorine + potassium iodide  potassium chloride + iodine Cl2(aq) + 2KI(aq)  2KCl(aq) + I2(aq) Bromine + potassium iodide  potassium bromide + iodine Br2(aq) + 2KI(aq)  2KBr(aq) + I2(aq)

Conclusion: From this experiment, it can be concluded that the reaction of group 7 halogens decreases down the group; where chlorine is more reactive than bromine and bromine is more reactive than Iodine....